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H syndrome (HS) is a rare autosomal recessive genodermatosis characterised by cutaneous hyper­pigmentation, hypertrichosis, sclerodermatous thickening, and multisystemic involvement. It results from mutations in the SLC29A3 gene encoding the human equilibrative nucleoside transporter 3, leading to impaired histiocyte apoptosis and unchecked proliferation. We report the case of a 24-year-old Moroccan male who had a history of insulin-dependent diabetes mellitus. He deve­loped hyperpigmented skin patches with hypertrichosis and induration. Musculoskeletal findings included bilateral hallux valgus, pes planus, reducible flexion contractures of the proximal interphalangeal joints, and restricted ankle dorsiflexion. Additional findings consist of lymphadenopathy, hepatomegaly, hypogonadism, and ophthalmic manifestations. Investigations showed elevated sedimentation rate, anaemia, and osteopaenia. Ankle ultrasound revealed calcaneal enthesopathy and subcutaneous infiltration. In reporting this case, we aim to highlight the significant rheumatological involvement that can arise in patients with H syndrome and explore potential treatment options to improve the musculoskeletal findings.

Abstract Background H Syndrome is a rare genetic condition caused by biallelic pathogenic variants in the SLC29A3 gene. It is characterized by a wide range of clinical manifestations, many of which are related to the immune-rheumatological field. These include scleroderma-like skin changes, deforming arthritis, and enlarged lymph nodes. The condition also features cardiac and endocrine defects, as well as hearing loss, for which the immune pathogenesis appears less clear. Immunomodulatory medications have been shown to improve many symptoms in recent experiences. Case presentation A 21-year-old girl was referred to our institute after being diagnosed with H syndrome. Her medical history was characterized by the development of finger and toe deformities, which developed since the first years of life and progressively worsened with clinodactyly. At 6 years of age, she was diagnosed with diabetes mellitus without typical autoantibodies and with bilateral sensorineural hearing loss. She also complained of frequent episodes of lymphadenopathy, sometimes with colliquation and growth retardation due to pancreatic insufficiency. It wasn’t until the genetic diagnosis of H syndrome that the continual increase in acute phase reactants was noticed, suggesting that an immunological pathogenesis may be the source of her problems. During her visit to our institute, she reported serious pain in both feet and hands and difficulty walking due to knee arthritis and muscle contractures. Conventional therapy with steroid injection in affected joints and methotrexate only led to partial improvement. After a thorough assessment of her inflammatory profile showing a high interferon score, the girl received treatment with baricitinib. Furthermore, based on recent data showing that SLC29A3 deficiency results in interferon production because of Toll-like Receptor 7 activation in lysosomes, hydroxychloroquine was also added. The combination of the two drugs resulted for the first time in a rapid and persistent normalization of inflammatory markers, paralleled by a dramatic improvement in symptoms. Conclusions We describe the results of inhibiting IFN inflammation in H syndrome and discuss how JAK inhibitors and antimalarials might represent a mechanistically based treatment for this orphan drug disorder.

Background: H Syndrome is a rare genetic condition caused by biallelic pathogenic variants in the SLC29A3 gene. It is characterized by a wide range of clinical manifestations, many of which are related to the immune-rheumatological field. These include scleroderma-like skin changes, deforming arthritis, and enlarged lymph nodes. The condition also features cardiac and endocrine defects, as well as hearing loss, for which the immune pathogenesis appears less clear. Immunomodulatory medications have been shown to improve many symptoms in recent experiences. Case presentation: A 21-year-old girl was referred to our institute after being diagnosed with H syndrome. Her medical history was characterized by the development of finger and toe deformities, which developed since the first years of life and progressively worsened with clinodactyly. At 6 years of age, she was diagnosed with diabetes mellitus without typical autoantibodies and with bilateral sensorineural hearing loss. She also complained of frequent episodes of lymphadenopathy, sometimes with colliquation and growth retardation due to pancreatic insufficiency. It wasn't until the genetic diagnosis of H syndrome that the continual increase in acute phase reactants was noticed, suggesting that an immunological pathogenesis may be the source of her problems. During her visit to our institute, she reported serious pain in both feet and hands and difficulty walking due to knee arthritis and muscle contractures. Conventional therapy with steroid injection in affected joints and methotrexate only led to partial improvement. After a thorough assessment of her inflammatory profile showing a high interferon score, the girl received treatment with baricitinib. Furthermore, based on recent data showing that SLC29A3 deficiency results in interferon production because of Toll-like Receptor 7 activation in lysosomes, hydroxychloroquine was also added. The combination of the two drugs resulted for the first time in a rapid and persistent normalization of inflammatory markers, paralleled by a dramatic improvement in symptoms. Conclusions: We describe the results of inhibiting IFN inflammation in H syndrome and discuss how JAK inhibitors and antimalarials might represent a mechanistically based treatment for this orphan drug disorder. [ABSTRACT FROM AUTHOR]

H syndrome is a rare autosomal recessive genetic disorder characterized by the following clinical features: cutaneous hyperpigmentation, hypertrichosis, hepatosplenomegaly, heart anomalies, hearing loss, hypogonadism, short stature, hallux valgus, hyperglycemia, fixed flexion contractures of the toe joints, and the proximal interphalangeal joints. In rare cases, autoinflammatory and lymphoproliferative manifestations have also been reported. This disorder is due to loss-of-function mutations in SLC29A3 gene, which encode the equilibrative nucleoside transporter ENT3. This deficiency leads to abnormal function and proliferation of histiocytes. H syndrome is part of the R-group of histiocytosis. We report two different cases, one was diagnosed in adulthood and the other in childhood. The first case reported is a 37-year-old woman suffering from H syndrome with an autoinflammatory systemic disease that begins in adulthood (fever and diffuse organ's infiltration) and with cutaneous, articular, auditory, and endocrinological manifestations since childhood. The second case reported is a 2-year-old girl with autoinflammatory, endocrine, and cutaneous symptoms (fever, lymphadenopathy, organomegaly, growth delay, and cutaneous hyperpigmentation). Homozygous mutations in SLC29A3 confirmed the diagnosis of H syndrome in both cases. Each patient was treated with Tocilizumab with a significant improvement for lymphoproliferative, autoinflammatory, and cutaneous manifestations. Both cases were reported to show the multiple characteristics of this rare syndrome, which can be diagnosed either in childhood or in adulthood. In addition, an overview of the literature suggested Tocilizumab efficiency. [ABSTRACT FROM AUTHOR]

H syndrome is a rare autosomal recessive genetic disorder characterized by the following clinical features: cutaneous hyperpigmentation, hypertrichosis, hepatosplenomegaly, heart anomalies, hearing loss, hypogonadism, short stature, hallux valgus, hyperglycemia, fixed flexion contractures of the toe joints, and the proximal interphalangeal joints. In rare cases, autoinflammatory and lymphoproliferative manifestations have also been reported. This disorder is due to loss-of-function mutations in SLC29A3 gene, which encode the equilibrative nucleoside transporter ENT3. This deficiency leads to abnormal function and proliferation of histiocytes. H syndrome is part of the R-group of histiocytosis. We report two different cases, one was diagnosed in adulthood and the other in childhood. The first case reported is a 37-year-old woman suffering from H syndrome with an autoinflammatory systemic disease that begins in adulthood (fever and diffuse organ’s infiltration) and with cutaneous, articular, auditory, and endocrinological manifestations since childhood. The second case reported is a 2-year-old girl with autoinflammatory, endocrine, and cutaneous symptoms (fever, lymphadenopathy, organomegaly, growth delay, and cutaneous hyperpigmentation). Homozygous mutations in SLC29A3 confirmed the diagnosis of H syndrome in both cases. Each patient was treated with Tocilizumab with a significant improvement for lymphoproliferative, autoinflammatory, and cutaneous manifestations. Both cases were reported to show the multiple characteristics of this rare syndrome, which can be diagnosed either in childhood or in adulthood. In addition, an overview of the literature suggested Tocilizumab efficiency.

Dysosteosclerosis (DSS), the term coined in 1968 for ultrarare dysplasia of the skeleton featuring platyspondyly with focal appendicular osteosclerosis, has become generic by encompassing the genetic heterogeneity recently reported for this phenotype. We studied four unrelated Turkish patients with DSS to advance understanding of the new nosology. Patient 1 suffered femur fractures beginning at age 1 year. DSS was suspected from marked metaphyseal osteosclerosis in early childhood and subsequently platyspondyly accompanying patchy osteosclerosis of her appendicular skeleton. She harbored in SLC29A3, in 2012 the first gene associated with DSS, a unique homozygous duplication (c.303_320dup, p.102_107dupYFESYL). Patient 2 presented similarly with fractures and metaphyseal osteosclerosis but with no platyspondyly at age 2 months. She was homozygous for a novel nonsense mutation in SLC29A3 (c.1284C>G, p.Tyr428*). Patient 3 had ocular disease at age 2 years, presented for short stature at age 11 years, and did not begin to fracture until age 16 years. Radiographs showed mild platyspondyly and focal metaphyseal and femoral osteosclerosis. She was homozygous for a unique splice site mutation in TNFRSF11A (c.616+3A>G). Patient 4 at age 2 years manifested developmental delay and frequent infections but did not fracture. He had unique metadiaphyseal splaying and osteosclerosis, vertebral end‐plate osteosclerosis, and cortical thinning of long bones but no mutation was detected of SLC29A3, TNFRSF11A, TCIRG1, LRRK1, or CSF1R associated with DSS. We find that DSS from defective SLC29A3 presents earliest and with fractures. DSS from compromised TNFRSF11A can lead to optic atrophy as an early finding. Negative mutation analysis in patient 4 suggests further genetic heterogeneity underlying the skeletal phenotype of DSS. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research. [ABSTRACT FROM AUTHOR]

Agenesis of the inferior vena cava in H syndrome due to a novel SLC29A3 mutation. Keywords: H syndrome; mutation; SLC29A3; Indian; hyperpigmented plaques EN H syndrome mutation SLC29A3 Indian hyperpigmented plaques e138 e140 3 02/23/23 20230301 NES 230301 Dear Editor, H syndrome is a rare autosomal recessive disorder with a characteristic array of features such as hyperpigmentation, hypertrichosis, short height, hypogonadism, hepatosplenomegaly, hyperglycemia, hearing loss, and heart anomalies. [Extracted from the article]

H syndrome is a rare autosomal recessive disorder with clinical features comprising: hyperpigmentation, hypertrichosis, hearing loss, heart anomalies, low height, hypogonadism and hepatosplenomegaly. H syndrome results from loss‐of‐function mutations in SLC29A3 which leads to abnormal proliferation and function of histiocytes. Herein, we discuss the considerable phenotypic heterogeneity detected in a consanguineous Egyptian family comprising of four affected siblings, two of which are monozygotic twin and the possible therapeutics. The phenotypic variability may be attributed to the role of histiocytes in the tissue response to injury. Such variable expressivity of H syndrome renders the diagnosis challenging and delays the management. The different treatment approaches used for this rare entity are reviewed. [ABSTRACT FROM AUTHOR]

Glucokinase-Maturity-Onset Diabetes of the Young (GCK -MODY) is characterized by asymptomatic, non-progressive and fasting hyperglycemia, albeit not without phenotypic variability. We used next generation sequencing (NGS) to screen for 34 MODY genes in a non-obese person with familial young-onset diabetes followed by screening in 24 family members within three generations with varying presentations of young-onset diabetes and sensorineural hearing loss. The index patient was found to carry a paternally-inherited heterozygous missense variant (c.716 A>G) of GCK in exon 7 with amino acid change (Q239R). This variant was associated with phenotypic heterogeneity ranging from normal glucose tolerance to diabetes with complications amongst the siblings which might be modified by obesity and chronic hepatitis B infection. Two paternally-inherited variants of SLC29A3 encoding a nucleoside transporter protein and Apo-A1 genes also co-segregated with glucose and lipid traits. Co-occurrence of diabetes and deafness in maternal aunts led to discovery of WFS1 (Wolfram syndrome type 1) as a cause of non-syndromic deafness in multiple members of the maternal pedigree. Our findings highlight the complex causes of familial young-onset diabetes and the need of a multidisciplinary approach to interpret the clinical relevance of discoveries made by NGS in this era of genomic medicine. [ABSTRACT FROM AUTHOR]

Glucokinase-Maturity-Onset Diabetes of the Young (GCK-MODY) is characterized by asymptomatic, non-progressive and fasting hyperglycemia, albeit not without phenotypic variability. We used next generation sequencing (NGS) to screen for 34 MODY genes in a non-obese person with familial young-onset diabetes followed by screening in 24 family members within three generations with varying presentations of young-onset diabetes and sensorineural hearing loss. The index patient was found to carry a paternally-inherited heterozygous missense variant (c.716 A>G) of GCK in exon 7 with amino acid change (Q239R). This variant was associated with phenotypic heterogeneity ranging from normal glucose tolerance to diabetes with complications amongst the siblings which might be modified by obesity and chronic hepatitis B infection. Two paternally-inherited variants of SLC29A3 encoding a nucleoside transporter protein and Apo-A1 genes also co-segregated with glucose and lipid traits. Co-occurrence of diabetes and deafness in maternal aunts led to discovery of WFS1 (Wolfram syndrome type 1) as a cause of non-syndromic deafness in multiple members of the maternal pedigree. Our findings highlight the complex causes of familial young-onset diabetes and the need of a multidisciplinary approach to interpret the clinical relevance of discoveries made by NGS in this era of genomic medicine.

Abstract Background The SLC29A3 gene, encoding a nucleoside transporter protein, is found in intracellular membranes. Based on the literatures, mutations in this gene cause a wide range of clinical manifestations including H syndrome, pigmented hypertrichosis with insulin dependent diabetes, Faisalabad histiocytosis, and dysosteosclerosis. However, all these disorders with their different names and terminologies are actually the same entity termed H syndrome. Case presentation We report four GJB2 and GJB6 negative deaf patients from two Iranian related families who present the associated symptoms of SLC29A3-disorder. Whole Exome Sequencing (WES) using Next Generation Illumina Sequencing was used to enrich all exons of protein-coding genes as well as some other important genomic regions in one of studied patients. A novel homozygous frame-shift mutation c.307-308delTT (p.Phe103fs) in exon 3 of SLC29A3 gene was identified in a 35 years old man with profound hearing loss, camptodactyly, rheumatoid arthritis and delayed puberty without any skin changes, short stature and insulin dependent diabetes mellitus. The mutation found was also confirmed by Sanger sequencing in other studied patients and their healthy parents. In compared to proband, however the clinical manifestations of these patients were different, indicating variable expressivity of mutant SLC29A3 gene as well as possible involvement of other modifier genes. Conclusion The present study uncovered a rare novel homozygous frame-shift mutation c.307-308delTT in SLC29A3 gene of four related patients with various manifestation of SLC29A3-disorder. Such studies can help to conduct genetic counseling and subsequently, prenatal diagnosis more accurately for individuals at the high risk of these types of genetic disorders.

Background: H syndrome is a multisystem inflammatory disease caused by mutations in the SLC29A3 gene (OMIM #602782). The protein product, hENT3, is a nucleoside transporter essential for DNA salvage synthesis. Clinical manifestations are hyperpigmentation, hypertrichosis, hepatosplenomegaly, hearing loss, heart anomalies, hypogonadism, short stature, skeletal deformities, and diabetes mellitus. Laboratory findings are consistent with inflammatory processes. Structural kidney anomalies have been described in 6% of patients. Case reports: Three family members with genetically diagnosed H syndrome (c.1279G>A, p.Gly427Ser). Two of them presented with hypoalbuminemia and nephrotic range proteinuria. Kidney ultrasound was normal. Kidney biopsy performed in one patient presenting with generalized peripheral pitting edema revealed membranous nephropathy. Different treatments including ACE inhibitors, corticosteroids, and immunomodulatory agents failed to improve the clinical outcome. Conclusions: Generalized peripheral pitting edema and glomerulopathy broaden the clinical spectrum of H syndrome. Periodic bloodwork and urinalysis are recommended. [ABSTRACT FROM AUTHOR]

Objective: This study aims to identify causal variants associated with vitiligo in an expanded region of 10q22.1. Materials and Methods: We conducted a fine-scale deep analysis of the expanded 10q22.1 region using in a large genome-wide association studies dataset consisting of 1117 cases and 1701 controls through imputation. We selected five nominal coding single nucleotide polymorphisms (SNPs) located in SLC29A3 and CDH23 and genotyped them in an independent cohort of 2479 cases and 2451 controls in a Chinese Han population cohort using the Sequenom MassArray iPLEX1 system. Results: A missense SNP in SLC29A3 , rs2252996, showed strong evidence of association with vitiligo ( p  = 1.34 × 10 -8 , odds ratio [OR] = 0.82). Three synonymous SNPs (rs1084004 in SLC29A3 ; rs12218559 and rs10999978 in CDH23 ) provided suggestive evidence of association for vitiligo ( p  = 1.69 × 10 -6 , OR = 0.84; p  = 9.47 × 10 -5 , OR = 1.18; p  = 6.90 × 10 -4 , OR = 1.16, respectively). Stepwise conditional analyses identified two significant independent disease-associated signals from the four SNPs (both p  < 0.05; both D' = 0.03; and r 2  = 0.00). Conclusion: The study identifies four genetic coding variants in SLC29A3 and CDH23 on 10q22.1 that may contribute to vitiligo susceptibility with one missense variant affecting disease subphenotypes. The presence of multiple genetic variants underscores their significant role in the genetic pathogenesis of the disease.

H syndrome is a complex multi‐organ disorder with autosomal recessive inheritance. The skin manifestations include early onset hyperpigmentation and hypertrichosis, followed by skin induration often diagnosed as scleromyxedema and morphea. There is no effective treatment. Our objective was to study the efficacy of mycophenolate mofetil in a patient with genetically confirmed H syndrome. We sought the genetic cause of H syndrome with whole‐exome sequencing (WES) of the proband. Genome‐wide homozygosity mapping (HM) provided additional evidence for causality of the variant suggested by WES. Here, we report a patient with characteristic clinical features of H syndrome, and the diagnosis was confirmed by identification of a homozygous SLC29A3 mutation (p.Gly437Arg). The patient was initially treated with prednisolone and cyclosporine, but after development of side‐effects she was placed on mycophenolate mofetil. After the treatment with mycophenolate mofetil was initiated, resolution of hyperpigmentation was noted, and no new lesions developed during an 18‐month follow‐up period. Thus, mycophenolate mofetil could be considered as a safe and partially effective treatment of H syndrome. [ABSTRACT FROM AUTHOR]

H syndrome (OMIM 602782) is a recently defined autosomal recessive genodermatosis. Cutaneous findings of H syndrome include hyperpigmentation, hypertrichosis, and induration, while hearing loss, heart anomalies, hepatomegaly, hypogonadism, hyperglycemia (diabetes mellitus), low height (short stature), hallux valgus (flexion contractures), and hematological abnormalities are the extracutaneous abnormalities. We report a novel homozygous missense mutation, c.416T > C p.(Leu139Pro), in the SLC29A3 (NM_001174098.1) gene in two sisters with H syndrome presenting with different phenotypes. [ABSTRACT FROM AUTHOR]

The emphasis of our study was to determine the physiological function of miR‐1224‐5p in rectal cancer (RC) and its in‐depth mechanism. First, the expression of miR‐1224‐5p in RC tissues was analyzed using public data from the TCGA database. Then, miR‐1224‐5p expression in RC cell lines SW480 and SW837 was measured using the qRT‐PCR assay. The subsequent CCK‐8 assay was executed to assess the function of miR‐1224‐5p in the viability of the RC cell. Bioinformatics prediction prompted that SLC29A3 may be a potential target gene for miR‐1224‐5p. Western blotting and dual‐luciferase reporter assays were performed to affirm the above forecasting. Kaplan–Meier analysis and Cox multivariate analysis were carried out to assess the relationship between SLC29A3 and prognosis. Finally, CCK‐8, colony formation assay, and transwell assay were used for functional analysis of miR‐1224‐5p/ SLC29A3 axis in vitro. MiR‐1224‐5p was expressed at low levels in RC tissues and cell lines. Up‐regulation of miR‐1224‐5p inhibited SW480 cell viability, while inhibition of miR‐1224‐5p enhanced the viability of SW837 cells. What is more, we affirmed that miR‐1224‐5p could direct target SLC29A3, which was expressed at high levels in RC tissues. In addition, SLC29A3 could be used as an independent predictive factor of prognosis in patients with RC, and the higher SLC29A3 expression, the lower survival rate. Finally, cellular functional experiments evidenced that miR‐1224‐5p mimic can reduce the cell viability, invasion, and migration, while overexpression of SLC29A3 presented an opposite effect. Importantly, co‐transfection experiments indicated that SLC29A3 can reverse miR‐1224‐5p‐mediated inhibition in the malignant progression of RC cells. Our work raised the possibility that miR‐1224‐5p functioned as a tumor suppressor in RC, which achieved its function via targeting SLC29A3. [ABSTRACT FROM AUTHOR]

As a crucial gene associated with diseases, the SLC29A3 gene encodes the equilibrative nucleoside transporter 3 (ENT3). ENT3 plays an essential regulatory role in transporting intracellular hydrophilic nucleosides, nucleotides, hydrophilic anticancer and antiviral nucleoside drugs, energy metabolism, subcellular localization, protein stability, and signal transduction. The mutation and inactivation of SLC29A3 are intimately linked to the occurrence, development, and prognosis of various human tumors. Moreover, many hereditary human diseases, such as H syndrome, pigmentary hypertrichosis and non-autoimmune insulin-dependent diabetes mellitus (PHID) syndrome, Faisalabad histiocytosis (FHC), are related to SLC29A3 mutations. This review explores the mechanisms of SLC29A3 mutations and expression alterations in inherited disorders and cancers. Additionally, we compile studies on the inhibition of ENT3, which may serve as an effective strategy to potentiate the anticancer activity of chemotherapy. Thus, the synopsis of genetics, permeant function and drug therapy of ENT3 provides a new theoretical and empirical foundation for the diagnosis, prognosis of evaluation and treatment of various related diseases. [ABSTRACT FROM AUTHOR]

Abstract Background H Syndrome is an autosomal recessive disorder characterized by cutaneous hyperpigmentation, hypertrichosis, and induration with numerous systemic manifestations. The syndrome is caused by mutations in SLC29A3, a gene located on chromosome 10q23, which encodes the human equilibrative transporter 3 (hENT3). Less than 100 patients with H syndrome have been described in the literature, with the majority being of Arab descent, and only a few from North America. Case presentation Here we report five pediatric patients from three medical centers in the United States who were identified to have H syndrome by whole exome sequencing. These five patients, all of whom presented to pediatric rheumatologists prior to diagnosis, include two of Northern European descent, bringing the total number of Caucasian patients described to three. The patients share many of the characteristics previously reported with H syndrome, including hyperpigmentation, hypertrichosis, short stature, insulin-dependent diabetes, arthritis and systemic inflammation, as well as some novel features, including selective IgG subclass deficiency and autoimmune hepatitis. They share genetic mutations previously described in patients of the same ethnic background, as well as a novel mutation. In two patients, treatment with prednisone improved inflammation, however both patients flared once prednisone was tapered. In one of these patients, treatment with tocilizumab alone resulted in marked improvement in systemic inflammation and growth. The other had partial response to prednisone, azathioprine, and TNF inhibition; thus, his anti-TNF biologic was recently switched to tocilizumab due to persistent polyarthritis. Another patient improved on Methotrexate, with further improvement after the addition of tocilizumab. Conclusion H syndrome is a rare autoinflammatory syndrome with pleiotropic manifestations that affect multiple organ systems and is often mistaken for other conditions. Rheumatologists should be aware of this syndrome and its association with arthritis. It should be considered in patients with short stature and systemic inflammation, particularly with cutaneous findings. Some patients respond to treatment with biologics alone or in combination with other immune suppressants; in particular, treatment of systemic inflammation with IL-6 blockade appears to be promising. Overall, better identification and understanding of the pathophysiology may help devise earlier diagnosis and better treatment strategies.

Nucleic acid (NA)-sensing Toll-like receptors (TLRs) reside in the endosomal compartment of innate immune cells, such as macrophages and dendritic cells. NAs transported to the endosomal compartment are degraded by DNases and RNases. Degradation products, including single-stranded DNA, oligoRNA, and nucleosides, are recognized by TLR7, TLR8, and TLR9 to drive the defense responses against pathogens. NA degradation influences endosomal TLR responses by generating and degrading TLR ligands. TLR ligand accumulation because of impaired NA degradation causes constitutive TLR activation, leading to autoinflammatory and autoimmune diseases. Furthermore, some genes associated with these diseases promote endosomal TLR responses. Therefore, endosomal TLRs are promising therapeutic targets for TLR-mediated inflammatory diseases, and novel drugs targeting TLRs are being developed., (© 2024. The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.)

Abstract The osteopetroses and related sclerosing bone dysplasias can have a broad range of manifestations. Especially in the milder forms, sandwich vertebrae are an easily recognizable and reliable radiological hallmark. We report on four patients from three families presenting with sandwich vertebrae and platyspondyly. The long bone phenotypes were discordant with one patient showing modeling defects and patchy osteosclerosis, while the second displayed only metaphyseal sclerotic bands, and the third and fourth had extreme metaphyseal flaring with uniform osteosclerosis. Two of the four patients had experienced pathological fractures, two had developmental delay, but none showed cranial nerve damage, hepatosplenomegaly, or bone marrow failure. According to these clinical features the diagnoses ranged between intermediate autosomal recessive osteopetrosis and dysosteosclerosis. After exclusion of mutations in CLCN7 we performed gene panel and exome sequencing. Two novel mutations in SLC29A3 were found in the first two patients. In the third family a TCIRG1 C-terminal frameshift mutation in combination with a mutation at position +4 in intron 2 were detected. Our study adds two cases to the small group of individuals with SLC29A3 mutations diagnosed with dysosteosclerosis, and expands the phenotypic variability. The finding that intermediate autosomal recessive osteopetrosis due to TCIRG1 splice site mutations can also present with platyspondyly further increases the molecular heterogeneity of dysosteosclerosis-like sclerosing bone dysplasias. Highlights • We describe sclerotic bone dysplasia due to SLC29A3 mutations with a hitherto unrecognized phenotypic variability. • Intermediate autosomal recessive osteopetrosis with dramatic metaphyseal flaring can be due to TCIRG1 mutations. • Intermediate autosomal recessive osteopetrosis due to TCIRG1 mutations can present like dysosteosclerosis. • Dysosteosclerosis is clinically and molecularly more heterogeneous and less malignant than previously thought. [ABSTRACT FROM AUTHOR]

Background: H Syndrome is an autosomal recessive disorder characterized by cutaneous hyperpigmentation, hypertrichosis, and induration with numerous systemic manifestations. The syndrome is caused by mutations in SLC29A3, a gene located on chromosome 10q23, which encodes the human equilibrative transporter 3 (hENT3). Less than 100 patients with H syndrome have been described in the literature, with the majority being of Arab descent, and only a few from North America. Case presentation: Here we report five pediatric patients from three medical centers in the United States who were identified to have H syndrome by whole exome sequencing. These five patients, all of whom presented to pediatric rheumatologists prior to diagnosis, include two of Northern European descent, bringing the total number of Caucasian patients described to three. The patients share many of the characteristics previously reported with H syndrome, including hyperpigmentation, hypertrichosis, short stature, insulin-dependent diabetes, arthritis and systemic inflammation, as well as some novel features, including selective IgG subclass deficiency and autoimmune hepatitis. They share genetic mutations previously described in patients of the same ethnic background, as well as a novel mutation. In two patients, treatment with prednisone improved inflammation, however both patients flared once prednisone was tapered. In one of these patients, treatment with tocilizumab alone resulted in marked improvement in systemic inflammation and growth. The other had partial response to prednisone, azathioprine, and TNF inhibition; thus, his anti-TNF biologic was recently switched to tocilizumab due to persistent polyarthritis. Another patient improved on Methotrexate, with further improvement after the addition of tocilizumab. Conclusion: H syndrome is a rare autoinflammatory syndrome with pleiotropic manifestations that affect multiple organ systems and is often mistaken for other conditions. Rheumatologists should be aware of this syndrome and its association with arthritis. It should be considered in patients with short stature and systemic inflammation, particularly with cutaneous findings. Some patients respond to treatment with biologics alone or in combination with other immune suppressants; in particular, treatment of systemic inflammation with IL-6 blockade appears to be promising. Overall, better identification and understanding of the pathophysiology may help devise earlier diagnosis and better treatment strategies. [ABSTRACT FROM AUTHOR]

H syndrome (OMIM 602782) is a very rare autosomal recessive genodermatosis with multisystem involvement. Hallmarks of this disorder are juvenile onset and progressive, hyperpigmented, hypertrichotic lesions with histiocytic infiltration. Associated systemic manifestations form a long list, and there is high variability between patients. In some patients, dysmorphic and other systemic features may be so subtle that the disorder may readily be mistaken as an acquired skin disease and treated as such. Herein, we report a novel homozygous c.1339G>A (p.Glu447Lys) mutation in the SLC29A3 gene in a patient with skin-dominant presentation of H syndrome. Additionally, due to the present case, double superior vena cava can be added to the list of possible cardiovascular manifestations of H syndrome. [ABSTRACT FROM AUTHOR]

Dysosteosclerosis (DSS) refers to skeletal dysplasias that radiographically feature focal appendicular osteosclerosis with variable platyspondyly. Genetic heterogeneity is increasingly reported for the DSS phenotype and now involves mutations of SLC29A3 , TNFRSF11A , TCIRG1 , LRRK1 , and CSF1R. Typical radiological findings are widened radiolucent long bones with thin cortices yet dense irregular metaphyses, flattened vertebral bodies, dense ribs, and multiple fractures. However, the radiographic features of DSS evolve, and the metaphyseal and/or appendicular osteosclerosis variably fades with increasing patient age, likely due to some residual osteoclast function. Fractures are the principal presentation of DSS, and may even occur in infancy with SLC29A3 -associated DSS. Cranial base sclerosis can lead to cranial nerve palsies such as optic atrophy, and may be the initial presentation, though not observed with SLC29A3- associated DSS. Gene-specific extra-skeletal features can be the main complication in some forms of DSS such as CSF1R- associated DSS. Further genetic heterogeneity is likely, especially for X-linked recessive DSS and cases currently with an unknown genetic defect. Distinguishing DSS can be challenging due to variable clinical and radiological features and an evolving phenotype. However, defining the DSS phenotype is important for predicting complications, prognosis, and instituting appropriate health surveillance and treatment. [ABSTRACT FROM AUTHOR]

H syndrome is an autosomal recessive syndrome, which affects the skin and some vital organs, it is caused by mutations in the SLC29A3 gene, encoding the human equilibrative nucleoside transporter hENT3. This report describes a patient with typical features of H syndrome. Based on the patient's clinical features, SLC29A3 was selected for molecular investigation. Through direct sequencing, a compound heterozygous alteration in the SLC29A3 gene was found. The c.243delA frameshift mutation leading to a premature termination, resulting in a truncated protein, and a splice site mutation c.300+1G>C predicted to cause a splicing error. This contribution extends the clinical variability of compound heterozygous SLC29A3 mutations resulting in an additional multisystemic manifestation of the clinical spectrum of SLC29A3 disorders. [ABSTRACT FROM AUTHOR]

Background: H syndrome is an autosomal recessive histiocytosis with multisystemic involvement caused by mutations in theSLC29A3gene. The term H syndrome was coined to denote the major clinical findings which includehyperpigmentation,hypertrichosis,hearing loss,hepatosplenomegaly,hypogonadism,hyperglycemia/diabetes mellitus andhallux valgus/flexion contractures. Almost 100 individuals affected with this disorder have been reported, however, a thorough evaluation of the ophthalmologic features of H syndrome has not yet been performed. Materials and Methods: Ophthalmic examination of a 50-year-old male with H syndrome. Mutation analysis ofSLC29A3was also performed in this patient. Results: Ophthalmic findings included; shallow orbits with exorbitism, bilateral pterygium, limbal thickening, corneal arcus and cortical cataract. We also review ophthalmologic findings in previously reported H syndrome patients. Conclusions: The presence of dilated lateral scleral vessels, corneal arcus and shallow orbits should raise the suspicion of H syndrome, especially when seen in young age. [ABSTRACT FROM AUTHOR]

Background: H syndrome is an autosomal recessive genodermatosis with multisystem involvement caused by mutations in SLC29A3. Objective: We sought to investigate the clinical and molecular findings in 79 patients with this disorder. Methods: A total of 79 patients were included, of which 13 are newly reported cases. Because of the phenotypic similarity and molecular overlap with H syndrome, we included 18 patients with allelic disorders. For 31 patients described by others, data were gathered from the medical literature. Results: The most common clinical features (>45% of patients) were hyperpigmentation, phalangeal flexion contractures, hearing loss, and short stature. Insulin-dependent diabetes mellitus and lymphadenopathy mimicking Rosai-Dorfman disease were each found in approximately 20%. Additional systemic features were described in less than 15% of cases. Marked interfamilial and intrafamilial clinical variability exists. Twenty mutations have been identified in SLC29A3, with no genotype-phenotype correlation. Limitations: In the 31 patients described by others, data were collected from the medical literature. Conclusions: H syndrome is a multisystemic disease with clinical variability. Consequently, all SLC29A3-related diseases should be considered a single entity. Recognition of the pleomorphic nature of H syndrome is important for diagnosis of additional patients. [Copyright &y& Elsevier]

Abstract: The H syndrome (OMIM 612391) is an autosomal recessive disorder characterized by hyperpigmentation, hypertrichosis, histiocytosis and short stature. It is caused by mutations in the SLC29A3 gene, which encodes for the equilibrative nucleoside transporter 3 protein (ENT3), of still uncertain subcellular localisation. Here we report a new case of H syndrome with the novel mutation c.243delA, which has been concomitantly described by others [A. Bolze, A. Abhyankar, A.V. Grant, B. Patel, R. Yadav, M. Byun, D. Caillez, J.F. Emile, M. Pastor-Anglada, L. Abel, A. Puel, R. Govindarajan, L. de Pontual, J.L. Casanova, A mild form of SLC29A3 disorder: a frameshift deletion leads to the paradoxical translation of an otherwise noncoding mRNA splice variant, PLoS ONE 7 (2012) e29708]. Patient-derived primary skin fibroblasts and B-lymphoblastoid cell lines (B-LCL) were obtained and, although no differences were found in mRNA levels of ENT3, a significant increase in plasma membrane equilibrative transport activity was found in fibroblasts from the patient. Loss of function of key proteins implicated in nucleoside metabolism can lead to mitochondrial DNA (mtDNA) depletion syndromes (MDS). Measurement of respiratory chain complex activity revealed that mitochondrial function was unaltered. Neither fibroblasts nor B-LCL showed mtDNA depletion when compared with controls. Fibroblasts and B-LCL from the patient were not particularly protected when mitochondrial damage was induced using nucleoside-derived drugs susceptible to being transported by ENT3. Analysis of mtDNA amounts in tissues obtained at autopsy proved inconclusive with respect to mitochondrial involvement in the pathogenesis of this syndrome. Overall, the data do not support the inclusion of H syndrome among the MDS and these findings are compatible with its recent inclusion among the lysosomal storage diseases. [Copyright &y& Elsevier]

Background: H syndrome is a rare autosomal recessive genetic disorder which involves the skin and other systemic organs and is caused by mutations in the SLC29A3 gene. Objectives: To disclose the molecular basis of H syndrome in two Syrian families, and to determine the localization of hENT3 in human skin. Methods: DNA from two Syrian families with H syndrome was analyzed through direct sequencing, and the expression of hENT3 in normal human skin was investigated by in situ hybridization and immunostaining. Results: We identified two novel mutations in the SLC29A3 gene: a homozygous splice site mutation IVS1+2T>G predicted to cause a splicing error, and a homozygous missense mutation c.1157G>A (p.R386Q) which substituted highly conserved amino acid residue in a transmembrane domain of hENT3. Furthermore, we demonstrate that hENT3 is expressed in histiocytes as well as in endothelium of blood and lymphatic vessels in normal human skin. Conclusions: Our results further enhance the mutation spectrum of the SLC29A3 gene for this rare genetic disorder, and also suggest potential pathomechanisms for the skin lesions resulting from SLC29A3 mutations. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

We describe a case of H syndrome with massive skin involvement, retroperitoneal fibrosis and Raynaud's phenomenon. A 48-year-old man with parents of a consanguineous marriage, first appeared with decreased urine output, skin sclerosis on his inner thighs and short stature (142 cm, 47 kg). The patient had suffered from hearing loss since the age of 1 year, and his secondary sexual characteristics had not developed. Computed tomography showed periaortic fibrosis, bilateral ureteral stenosis, hydronephrosis and sclerosis of the germinal cords. A biopsy from the retroperitoneal mass revealed remarkable fibrosis with chronic inflammatory cells. Biopsies from the skin lesion showed thick collagen bundles through the dermis and lymphohistiocytic infiltration with numerous plasma cells. Serum inflammatory markers, such as C-reactive protein, vascular endothelial factor, transforming growth factor-β and soluble interleukin-2 receptor, were elevated. Prednisolone was effective in treating skin lesions and in lowering serum inflammatory markers. After a long period of follow up, genomic DNA of the patient was obtained, and we identified a homozygous mutation in exon 5, c.625G>A, which caused transition of glycine to arginine, p.Gly208Arg, in the patient, but not in DNA samples from another 50 healthy individuals. This is the first case of H syndrome with Raynaud's phenomenon and retroperitoneal fibrosis, and the first Japanese case of H syndrome reported in the English published work with a novel mutation in the SLC29A3 gene. [ABSTRACT FROM AUTHOR]

Abstract: In 2008, SLC29A3 has been implicated in a syndromic form of genodermatosis: H syndrome. The major features encountered in H syndrome are Hearing loss, Hyperglycaemia, Heart anomalies, Hypertrichosis, Hyperpigmentation, Hepatomegaly and Hypogonadism. More recently, SLC29A3 mutations have been described in families presenting syndromes associating generalized histiocytosis to systemic progressive features: severe camptodactyly, hearing loss, hypogonadism, hepatomegaly, heart defects and skin hyperpigmentation. We have identified a homozygous missense SLC29A3 mutation in a patient presenting with only a progressive sensorineural hearing impairment and a single cervical node (Rosai Dorfman). SLC29A3 mutations appear to be involved in a large phenotypic continuum which should prompt physicians to study this gene even in mild clinical presentations. [Copyright &y& Elsevier]

Abstract: This case report describes two patients with H syndrome, a multisystemic autosomal recessive disorder, caused by mutations in the SLC29A3 gene. It is characterized by cutaneous hyperpigmentation, camptodactyly or flexion contractures and other features, among them hearing loss. The two patients had hearing loss as their presenting symptom, and had mutations in SLC29A3, one of them a novel mutation. The aim of this paper is to increase awareness to this recently described disorder, and to emphasize that H syndrome should be included in the differential diagnosis of congenital or acquired syndromic hearing loss in children. [Copyright &y& Elsevier]

The H syndrome (OMIM 612391) is a recently described autosomal recessive disorder characterized by cutaneous hyperpigmentation, hypertrichosis, hepatosplenomegaly, heart anomalies, hearing loss, hypogonadism, short stature (low height), hyperglycaemia/diabetes mellitus, hallux valgus, and fixed flexion contractures of the toe and finger joints. 1,2 Histologically, there is an inflammatory infiltrate consisting mainly of histiocytes, later replaced by fibrosis of the deep dermis and subcutis. 3 In total, 31 patients have been reported in the literature with the clinical phenotype characteristic of this syndrome. 1–7 [ABSTRACT FROM AUTHOR]

An abstract of the article "H Syndrome: A Rare Monogenic Cause of Insulin-Dependent Diabetes Mellitus," by Zeynep Atay and colleagues is presented.

Skeletal dysplasias (SKD) with increased bone density form a discrete group of SKDs as per the Nosology and Classification of Genetic Skeletal Disorders, 2010 Revision. This group, with the prototype disorder being osteopetrosis, has evolved over the last century, with new entities being described & their molecular basis being increasingly elucidated. Osteopetrosis, which remained an enigma in the early part of its description, is now known to be genetically heterogenous. Other disorders in this group, which were initially described as variant forms of osteopetrosis, are now recognised to be distinct conditions. However, all these SKDs with increased bone density share their molecular pathogenesis as majority arise due to mutations in the genes governing osteoclast formation and function., (Copyright © 2013 Elsevier B.V. All rights reserved.)