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It's an inconvenient truth for all of us: Aging is not for the faint of heart. The hard realities of aging and the need to stay in a disciplined program [...]

Telomere biology disorders (TBDs) are a spectrum of multisystem inherited disorders characterized by bone marrow failure, resulting from mutations in the genes encoding telomerase or other proteins involved in maintaining telomere length and integrity. Pathogenicity of variants in these genes can be hard to evaluate, because TBD mutations show highly variable penetrance and genetic anticipation related to inheritance of shorter telomeres with each generation. Thus, detailed functional analysis of newly identified variants is often essential. Herein, we describe a patient with compound heterozygous variants in the TERTgene, which encodes the catalytic subunit of telomerase, hTERT. This patient had the extremely severe Hoyeraal-Hreidarsson form of TBD, although his heterozygous parents were clinically unaffected. Molecular dynamic modeling and detailed biochemical analyses demonstrate that one allele (L557P) affects association of hTERT with its cognate RNA component hTR, whereas the other (K1050E) affects the binding of telomerase to its DNA substrate and enzyme processivity. Unexpectedly, the data demonstrate a functional interaction between the proteins encoded by the two alleles, with wild-type hTERT rescuing the effect of K1050E on processivity, whereas L557P hTERT does not. These data contribute to the mechanistic understanding of telomerase, indicating that RNA binding in one hTERT molecule affects the processivity of telomere addition by the other molecule. This work emphasizes the importance of functional characterization of TERTvariants to reach a definitive molecular diagnosis for patients with TBD, and, in particular, it illustrates the importance of analyzing the effects of compound heterozygous variants in combination, to reveal interallelic effects.

Telomere biology disorders (TBDs) are a spectrum of multisystem inherited disorders characterized by bone marrow failure, resulting from mutations in the genes encoding telomerase or other proteins involved in maintaining telomere length and integrity. Pathogenicity of variants in these genes can be hard to evaluate, because TBD mutations show highly variable penetrance and genetic anticipation related to inheritance of shorter telomeres with each generation. Thus, detailed functional analysis of newly identified variants is often essential. Herein, we describe a patient with compound heterozygous variants in the TERT gene, which encodes the catalytic subunit of telomerase, hTERT. This patient had the extremely severe Hoyeraal-Hreidarsson form of TBD, although his heterozygous parents were clinically unaffected. Molecular dynamic modeling and detailed biochemical analyses demonstrate that one allele (L557P) affects association of hTERT with its cognate RNA component hTR, whereas the other (K1050E) affects the binding of telomerase to its DNA substrate and enzyme processivity. Unexpectedly, the data demonstrate a functional interaction between the proteins encoded by the two alleles, with wild-type hTERT rescuing the effect of K1050E on processivity, whereas L557P hTERT does not. These data contribute to the mechanistic understanding of telomerase, indicating that RNA binding in one hTERT molecule affects the processivity of telomere addition by the other molecule. This work emphasizes the importance of functional characterization of TERT variants to reach a definitive molecular diagnosis for patients with TBD, and, in particular, it illustrates the importance of analyzing the effects of compound heterozygous variants in combination, to reveal interallelic effects.

PUPs B-LONG evaluated the safety and efficacy of recombinant factor IX Fc fusion protein (rFIXFc) in previously untreated patients (PUPs) with hemophilia B. In this open-label, phase 3 study, male PUPs (age <18 years) with hemophilia B (≤2 IU/dL of endogenous factor IX [FIX]) were to receive treatment with rFIXFc. Primary end point was occurrence of inhibitor development, with a secondary end point of annualized bleed rate (ABR). Of 33 patients who received ≥1 dose of rFIXFc, 26 (79%) were age <1 year at study entry and 6 (18%) had a family history of inhibitors. Twenty-eight patients (85%) received prophylaxis; median dosing interval was 7 days, with an average weekly dose of 58 IU/kg. Twenty-seven patients (82%) completed the study. Twenty-one (64%), 26 (79%), and 28 patients (85%) had ≥50, ≥20, and ≥10 exposure days (EDs) to rFIXFc, respectively. One patient (3.03%; 95% confidence interval, 0.08% to 15.76%) developed a low-titer inhibitor after 11 EDs; no high-titer inhibitors were detected. Twenty-three patients (70%) had 58 treatment-emergent serious adverse events; 2 were assessed as related (FIX inhibition and hypersensitivity in 1 patient, resulting in withdrawal). Median ABR was 1.24 (interquartile range, 0.00-2.49) for patients receiving prophylaxis. Most (>85%) bleeding episodes required only 1 infusion for bleed resolution. In this first study reporting results with rFIXFc in pediatric PUPs with hemophilia B, rFIXFc was well tolerated, with the adverse event profile as expected in a pediatric hemophilia population. rFIXFc was effective, both as prophylaxis and in the treatment of bleeding episodes. This trial was registered at www.clinicaltrials.govas #NCT02234310.

Hemophilia is a rare congenital bleeding disorder that results from complete or partial deficiency of blood coagulation factor (F)VIII (hemophilia A) or FIX (hemophilia B) due to pathogenic variants in their coding genes. Hemophilia requires complex management. To date, there is no evidence-based clinical practice guideline on hemophilia treatment based on the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

The outcome of gene therapy in an infant with X-linked severe combined immunodeficiency (SCID-X1), which typically causes a lack of T and natural killer (NK) cells is reported. It is concluded that only partial immunological reconstitution was achieved, most likely because of the relatively low dose of gene-corrected CD34+ cells re-infused, although viral infection during the early phase of T-cell reconstruction and the infant's NK+ phenotype may also have exerted an effect.

To identify the molecular cause in five unrelated families with a distinct autosomal dominant ocular systemic disorder we called ROSAH syndrome due to clinical features of retinal dystrophy, optic nerve edema, splenomegaly, anhidrosis, and migraine headache.

There have been significant advances in the understanding of the management of inherited bleeding disorders in pregnancy since the last Australian Haemophilia Centre Directors’ Organisation (AHCDO) consensus statement was published in 2009. This updated consensus statement provides practical information for clinicians managing pregnant women who have, or carry a gene for, inherited bleeding disorders, and their potentially affected infants. It represents the consensus opinion of all AHCDOmembers; where evidence was lacking, recommendations have been based on clinical experience and consensus opinion. During pregnancy and delivery, women with inherited bleeding disorders may be exposed to haemostatic challenges. Women with inherited bleeding disorders, and their potentially affected infants, need specialised care during pregnancy, delivery, and postpartum, and should be managed by a multidisciplinary team that includes at a minimum an obstetrician, anaesthetist, paediatrician or neonatologist, and haematologist. Recommendations on management of pregnancy, labour, delivery, obstetric anaesthesia and postpartum care, including reducing and treating postpartum haemorrhage, are included. The management of infants known to have or be at risk of an inherited bleeding disorder is also covered. Key changes in this update include the addition of a summary of the expected physiological changes in coagulation factors and phenotypic severity of bleeding disorders in pregnancy; a flow chart for the recommended clinical management during pregnancy and delivery; guidance for the use of regional anaesthetic; and prophylactic treatment recommendations including concomitant tranexamic acid.

Introduction

The diagnosis of type 1 von Willebrand disease (VWD), the most common inherited bleeding disorder in humans, is greatly dependent on an accurate diagnosis of significant mucocutaneous bleeding. In a previous study, the authors modified the criteria of the International Society on Thrombosis and Haemostasis for significant mucocutaneous bleeding to a format, the Hospital for Sick Children (HSC) criteria, that was more applicable to diagnose significant mucocutaneous bleeding in children. To assess the reliability and reproducibility of classification of subjects as “bleeders” versus “non-bleeders” using a questionnaire for significant mucocutaneous bleeding targeted to children, 39 subjects interviewed for a previous HSC VWD study were reinterviewed for the current study. The original bleeding classification was confirmed in 80% of subjects interviewed for a second time, indicating that this method of classification is reproducible (κ = 0.65), with a “substantial” agreement among the investigators who reviewed the questionnaire responses (κ = 0.71). The validity and utility of the HSC questionnaire for primary screening of children with suspected mucocutaneous bleeding disorders merits assessment in further clinical studies.

We describe data on a 7-year-old girl with congenital dyserythropoietic anemia (CDA), who also had familial Mediterranean fever (FMF). Repeated transfusions required since the age of 6 months to treat her CDA led to iron overload and a persistently high ferritin level. Her relapsing FMF made effective iron chelation therapy very difficult. Consequently, at the age of 4 years, she underwent allogeneic, sibling bone marrow transplantation (BMT). During conditioning for her BMT, symptoms of FMF, including splenomegaly, arthritis, and recurrent abdominal pain, began to resolve and she was gradually weaned off colchicine. Now, 2 years after the transplantation, she remains free from FMF symptomatology and is off all immunosuppressants. This case demonstrates that symptoms of FMF can be alleviated by the therapy used during allogeneic BMT. In this patient it is likely that the missing factor in FMF is now being provided by granulocytes derived from the stem cells within transplanted bone marrow.

No relevant conflicts of interest to declare.

Off Label Use: Rituximab is a monoclonal antibody against CD20 that is being used for its immunomodulatory properties.

Autosomal dominant macrothrombocytopenias such as the May-Hegglin anomaly, Sebastian syndrome, Fechtner syndrome and Epstein syndrome are all characterized by mutations in the MYH9gene. It has been proposed that these MYH9-related diseases are not distinct entities but represent a variable expression of a single disorder with a continuous clinical spectrum varying from mild macrothrombocytopenia with leukocyte inclusions to more severe conditions encompassing hearing loss, cataracts and renal failure. Mutations in the MYH9gene cause abnormal expression and/or function of the 224 kDa nonmuscle myosin heavy chain IIA (NMMHC-IIA) protein. Class II myosins are hexameric complexes composed of 2 heavy chains and 2 pairs of light chains forming a structure containing 2 N-terminal globular domains and an elongated α-helical C-terminal tail. Since identical mutations in the MYH9gene cause variable clinical presentations in different patients, other factors likely modulate the mutant phenotype. We describe a patient with congenital macrothrombocytopenia, mild bleeding problems, Döhle-like leukocyte inclusion bodies, normal hearing, normal renal function and absent cataracts. The patient has macrothrombocytes with an average manual platelet count of 100 x 109/L. Immunofluorescence confocal microscopy using an antibody specific for NMMHC-IIA revealed unique localization of NMMHC-IIA in the patient's leukocytes. Platelets and leukocytes from both parents and one sister are normal. Megakaryocytes cultured from the patient's and one parent's peripheral blood CD34+ cells also demonstrated abnormal distribution of NMMHC-IIA in only the patient's megakaryocytes. Ultrastructural analysis using electron microscopy revealed distinct inclusion bodies in the patient's leukocytes and megakaryocytes that were not observed in either parent. The patient's macrothrombocytopenia together with the abnormal distribution of NMMHC-IIA within leukocytes is highly suggestive of a MYH9-related disorder. The absence of these findings in either parent suggested a de novo MYH9mutation. We therefore sought to identify the mutation via amplification and DNA sequencing of all MYH9exons and intron/exon boundaries. Exons 1, 10, 16, 24, 25, 26, 30, 38 and 40 representing all of the previously described mutations in MYH9-related disorders were found to be normal. Surprisingly, the remaining MYH9gene exons and intron/exon boundaries were also normal. This unexpected finding suggests that another factor is involved in the normal assembly and/or localization of NMMHC-IIA in human leukocytes and megakaryocytes. It also suggests that a deficiency of this factor may lead to congenital macrothrombocytopenia with features indistinguishable from those of MYH9-related disorders. Identification of this factor could enhance our understanding of NMMHC-IIA-related congenital macrothrombocytopenias and would allow us to gain insights into the normal assembly and/or function of NMMHC-IIA in human megakaryocytes and platelets.