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Mucolipidosis II α/beta (MLII) is an autosomal recessive disease in which a gene mutation leads to improper targeting of lysosomal enzymes with an end result of accumulation of lysosomes in the mitochondria resulting in a dysfunctional mitochondria.1 Leigh syndrome (LS) is a rare progressive neurodegenerative disorder associated with dysfunctional mitochondria and oxidative phosphorylation.4 Both disease processes typically present in infancy.3 7 Herein, we present a case of an infant diagnosed with both mucolipidosis II and Leigh syndrome. Genetic analysis in this case revealed two mutations (NDUFA12 c.178C > T p.Arg60* and GNPTAB c.732_733delAA) on the long arm of chromosome 12 as the etiology of MLII and LS in this neonate, respectively. We are unaware of any previously published cases of the presence of these two diseases occurring in the same patient. The complex clinical presentation of this case led to a delay in the diagnosis, and we believe that the clinical phenotypes of these two conditions were likely worsened. The genetic alterations presented in this case occurred as a result of mutations on chromosome 12. We suggest further investigation into the potential overlap in the pathophysiology, specifically the inheritance pattern, linkage disequilibrium, mitochondrial–lysosomal interaction, or crosstalk contributing to both diseases.

Background Mucolipidosis type II (MLII) is an ultra-rare lysosomal storage disorder caused by defective lysosomal enzyme trafficking. Clinical hallmarks are craniofacial dysmorphia, cardiorespiratory dysfunction, hepatosplenomegaly, skeletal deformities and neurocognitive retardation. Death usually occurs in the first decade of life and no cure exists. Hematopoietic stem cell transplantation (HSCT) has been performed in few MLII patients, but comprehensive follow-up data are extremely scarce. Methods MLII diagnosis was confirmed in a female three-month-old patient with the mutations c.2213C > A and c.2220_2221dup in the GNPTAB gene. At nine months of age, the patient received HSCT from a 9/10 human leukocyte antigen (HLA)-matched unrelated donor. Results HSCT resulted in a sustained reduction of lysosomal storage und bone metabolism markers. At six years of age, the patient showed normal cardiac function, partial respiratory insufficiency and moderate hepatomegaly, whereas skeletal manifestations had progressed. However, the patient could walk and maintained an overall good quality of life. Neurocognitive testing revealed a developmental quotient of 36%. The patient died at 6.6 years of age following a human metapneumovirus (hMPV) pneumonia. Conclusions The exact benefit remains unclear as current literature vastly lacks comparable data on MLII natural history patients. In order to evaluate experimental therapies, in-depth prospective studies and registries of untreated MLII patients are indispensable., Graphical abstract Unlabelled Image

Mucolipidosis II and III (ML II/III) are caused by a deficiency of uridine-diphosphate N-acetylglucosamine: lysosomal-enzyme-N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase, EC2.7.8.17), which tags lysosomal enzymes with a mannose 6-phosphate (M6P) marker for transport to the lysosome. The process is performed by a sequential two-step process: first, GlcNAc-1-phosphotransferase catalyzes the transfer of GlcNAc-1-phosphate to the selected mannose residues on lysosomal enzymes in the cis-Golgi network. The second step removes GlcNAc from lysosomal enzymes by N-acetylglucosamine-1-phosphodiester α-N-acetylglucosaminidase (uncovering enzyme) and exposes the mannose 6-phosphate (M6P) residues in the trans-Golgi network, in which the enzymes are targeted to the lysosomes by M6Preceptors. A deficiency of GlcNAc-1-phosphotransferase causes the hypersecretion of lysosomal enzymes out of cells, resulting in a shortage of multiple lysosomal enzymes within lysosomes. Due to a lack of GlcNAc-1-phosphotransferase, the accumulation of cholesterol, phospholipids, glycosaminoglycans (GAGs), and other undegraded substrates occurs in the lysosomes. Clinically, ML II and ML III exhibit quite similar manifestations to mucopolysaccharidoses (MPSs), including specific skeletal deformities known as dysostosis multiplex and gingival hyperplasia. The life expectancy is less than 10 years in the severe type, and there is no definitive treatment for this disease. In this review, we have described the updated diagnosis and therapy on ML II/III.

Mucolipidosis type II (ML II) is an autosomal recessive lysosomal targeting disorder that may present with features of hyperparathyroidism. The aim of this study was to describe in detail the clinical cases of ML II presenting to a tertiary referral centre with biochemical and/or radiological features of hyperparathyroidism. There were twenty-three children diagnosed with ML II in the Republic of Ireland from July 1998 to July 2021 inclusive (a 23-year period). The approximate incidence of ML II in the Republic of Ireland is, therefore, 1 per 64,000 live births. Medical records were available and were reviewed for 21 of the 23 children. Five of these had been identified as having biochemical and/or radiological features of hyperparathyroidism. Of these five, three children were born to Irish Traveller parents and two to non-Traveller Irish parents. All five children had radiological features of hyperparathyroidism (on skeletal survey), with evidence of antenatal fractures in three cases and an acute fracture in one. Four children had biochemical features of secondary hyperparathyroidism. Three children received treatment with high dose Vitamin D supplements and two who had antenatal/acute fractures were managed with minimal handling. We observed resolution of secondary hyperparathyroidism in all cases irrespective of treatment. Four of five children with ML II and hyperparathyroidism died as a result of cardiorespiratory failure at ages ranging from 10 months to 7 years. Biochemical and/or radiological evidence of hyperparathyroidism is commonly identified at presentation of ML II. Further studies are needed to establish the pathophysiology and optimal management of hyperparathyroidism in this cohort. Recognition of this association may improve diagnostic accuracy and management, facilitate family counseling and is also important for natural history data.

Traditional approaches to prenatal genetic diagnosis for common presentations such as short femurs or intrauterine growth restriction are imperfect, and whole-exome sequencing is an emerging option. Mucolipidosis type II (I-cell disease) is an ultra-rare autosomal recessive lysosomal storage disorder with the potential for prenatal-onset skeletal and placental manifestations. We describe the prenatal signs in two recent unrelated patients with confirmed diagnoses soon after birth. In both cases, parents were consanguineous but there was no known family history of mucolipidosis type II. False reassurance was provided after negative testing for another disease with overlapping prenatal manifestations already present in one of the families, emphasizing that offspring of consanguineous parents can be at risk for more than one recessive condition. Our experience illustrates the potential advantages in expanding prenatal applications of WES for the identification of rare single gene disorders in offspring of consanguineous unions.

The article is devoted to a rare pathology from a group of accumulation diseases with an autosomal recessive type of inheritance – mucolipidosis II and IIIA types. The disease is characterized by a greater phenotypic similarity to mucopolysaccharidosis. Objective: analysis of genophenotypic parameters in Russian patients with mucolipidosis II and IIIA types. The activity of lysosomal enzymes in plasma (β-glucuronidase, total hexosaminidase and N-acetyl-α-D-glucosaminidase) was measured using a standard technique using chromogenic and fluorogenic substrates. Genomic DNA of peripheral blood leukocytes was isolated using a set of reagents Preb 100 (DIAtomTM). Amplification of all exons of the GNPTAB gene was carried out by polymerase chain reaction (PCR) followed by direct non-radioactive sequencing by Sanger. 50 patients aged from 1.5 to 10 years were examined. The clinical symptoms of the disease included: a Hurler-like phenotype, growth retardation, skeletal, cardiac and vascular damage, and CNS. Mucolipidosis type II (I-cell disease) was characterized by a more severe course. The clinical diagnosis was confirmed by the results of laboratory methods of investigation: normal parameters of renal excretion of glycosiminoglycans (GAG), high (5-15 times higher than normal) activity of lysosomal hydrolases in blood plasma and detection of mutations in the GNPTAB gene. 35 probands are completely genotyped. In 8 patients only 8 mutant alleles were detected; 7 mutations were not detected. Six new mutations in exons 1 (p.I31N; p.Q36P), 10 (p.L398P), 11 (p.W446X) and 13 (p.S738X; c.2250delT) were found, including a frequent mutation for Russian patients P.S738X (21% alleles). The most common (31.4% alleles) in the Russian cohort of patients was a known small deletion c. 3503_3504delTC, leading to a reading frameshift. A clinical observation of a child with type 2 mucolipidosis (I-cell disease) with typical symptomatology of the disease caused by two nonsense mutations of the GNPTAB gene is presented: p.S738X / p.R375X. In conclusion, it is emphasized that the identification of mutations of the GNPTAB gene provides prediction of the severity of the disease course, an understanding of the mechanisms of its development that will contribute to the development of pathogenetic treatment methods, improving the quality of life of patients and effective medical and genetic counseling.

Mucolipidosis type II (MLII) is a rare lysosomal storage disorder caused by defective trafficking of lysosomal enzymes. Severe skeletal manifestations are a hallmark of the disease including hip dysplasia. This study aims to describe hip morphology and the natural course of hip pathologies in MLII by systematic evaluation of plain radiographs, ultrasounds and magnetic resonance imaging (MRI). An international two-centered study was performed by retrospective chart review. All MLII patients with at least one pelvic radiograph were included. A total of 16 patients were followed over a mean of 3.5 years (range 0.2−10.7 years). Typical age-dependent radiographic signs identified were femoral cloaking (7/16), rickets/hyperparathyroidism-like changes (6/16) and constrictions of the supra-acetabular part of the os ilium (16/16) and the femoral neck (7/16). The course of acetabular and migration indexes (AI, MI) significantly increased in female patients. However, in the overall group, there was no relevant progression of acetabular dysplasia with a mean AI of 23.0 (range 5°−41°) and 23.7° (range 5°−40°) at the first and last assessments, respectively. Better knowledge on hip morphology in MLII could lead to earlier diagnosis, improved clinical management and enables assessment of effects of upcoming therapies on the skeletal system.

Mucolipidosis type II (I-Cell disease) is a rare autosomal recessive lysosomal disorder, resulting from functional deficiency of lysosomal enzymes due to an impaired targeting of the enzymes to lysosomes, which leads to an abnormal cell architecture and the overflow of lysosomal enzymes into the body fluids. The life expectancy of the patients is poor, with multisystem deterioration leading to death in early childhood. According to the available reports, patients with I-cell disease do not survive beyond the first decade of life. Here, we describe and illustrate various radiological-musculoskeletal manifestations of a rare case of mucolipidosis II who has been a survivor up to now, 20 years old. The course of her disease has been complicated by early severe visual compromise due to optic nerve swelling, hearing loss and mitral valve regurgitation/stenosis, bilateral carpal tunnel, and severe growth impairment. Our case demonstrates several skeletal features of dysostosis multiplex. At the age of 20, she is wheelchair bound and her medical course is complicated by recurrent pneumonia, treated with multiple hospitalizations, antibiotics, and BiPAP. She is on outpatient palliative care, Do Not Resuscitate/Do Not Intubate (DNR/DNI) status.Mukolipidoza typu II (I komórkowa choroba) jest rzadkim zaburzeniem lizosomalnym dziedziczonym autosomalnie recesywnie, wynikającym z niedobórów funkcjonalnych enzymów lizosomalnych spowodowanych zaburzeniami. Prognoza przeżywalności pacjentów jest zła. Liczne zaburzenia prowadzą do śmierci we wczesnym dzieciństwie. W aktualnej literaturze nie znaleziono opisu pacjenta żyjącego dłużej niż 10 lat. Przedstawiamy opis pacjentki, która przeżyła 20 lat z radiologiczno-mięśniowoszkieletową postacią rzadkiego schorzenia mukolipidozy II. Przebieg schorzenia jest skomplikowany wczesnymi zaburzeniami wynikającymi z obrzęku nerwu wzrokowego, ubytku słuchu stenozą mitralną, dwustronnym kanałem nadgarstka oraz ciężkimi zaburzeniami wzrastania. Pacjentka prezentuje ciężkie zaburzenia szkieletowe dyzostozy rozsianej. W wieku 20 lat pacjentka nie chodzi (porusza się na wózku). Medyczny przebieg choroby jest wikłany nawracającymi zapalenia płuc, wymagającymi wielokrotnie hospitalizacji, leczona antybiotykami i BiPAP. Znajduje się w opiece paliatywnej w statusie DNR/DNI (nie reanimować, nie intubować).

Inclusion cell disease (I-cell) is a rare autosomal recessive metabolic disease involving multiple organ systems, associated with a severely restricted life expectancy. No curative therapy is currently available, with management aimed at symptom palliation.We present a retrospective, single-centre, case series of children referred to a tertiary paediatric metabolic service. The clinical presentation, demographics, genetics and natural history of the condition are investigated.Five patients with I-cell disease were referred over a 10-year period. All patients were born with dysmorphic features and had a family history of I-cell disease on further exploration. Phenotypic variation was seen within patients with the same genetic profile. Airway problems were common with 100% of the documented sleep oximetry studies suggesting sleep-disordered breathing. Of the two patients who had tracheal intubation anaesthetic difficulties we encountered, one required intraoperative reintubation, and one suffered a failed intubation with subsequent death. All five patients required oxygen therapy with the use of CPAP and BiPAP also seen. Feeding issues were almost universal with four of the five patients requiring nasogastric feeding. Four patients had died in the 10-year period with a mean life expectancy of 36 months. Cause of death for three of the four patients was respiratory failure.Airway problems, including sleep-disordered breathing, were ubiquitous in this cohort of children. Any intervention requiring a general anaesthetic needs careful multidisciplinary consideration due to significant associated risks and possibly death. Management as a result is generally non-surgical and symptomatic. This case series demonstrates universal involvement of the airway and respiratory systems, an important consideration when selecting meaningful outcomes for future effectiveness studies of novel therapies.

Mucopolysaccharidosis (MPS) and Mucolipidosis (ML) share common phenotypes (coarse facial features, organomegaly, dysostosis multiplex) despite having different molecular basis. Thus, they pose great diagnostic challenge to treating clinicians. Differentiating between the two conditions requires a battery of tests from screening to molecular diagnosis. Besides discussing differential diagnosis of MPS like features with negative urinary Glycosaminoglycans (GAG), the authors also discuss the utility of p-nitrocatechol sulphate based chemical test as an important screening tool, besides establishing molecular basis in index case. Coutinho MF is grantee from the FCT (SFRH/BPD/101965/2014). info:eu-repo/semantics/publishedVersion

医学部小児科学教室 大澤眞木子教授退任記念特別号

Multiple sulfatase deficiency (MSD), mucolipidosis (MIL) II/III and Niemann-Pick type C1 (NPC1) disease are rare but fatal lysosomal storage disorders caused by the genetic defect of non-lysosomal proteins. The NPC1 protein mainly localizes to late endosomes and is essential for cholesterol redistribution from endocytosed LDL to cellular membranes. NPC1 deficiency leads to lysosomal accumulation of a broad range of lipids. The precise functional mechanism of this membrane protein, however, remains puzzling. ML II, also termed I cell disease. and the less severe ML III result from deficiencies of the Golgi enzyme N-acetylglucosamine 1-phosphotransferase leading to a global defect of lysosome biogenesis. In patient cells, newly synthesized lysosomal proteins are not equipped with the critical lysosomal trafficking marker mannose 6-phosphate, thus escaping from lysosomal sorting at the trans Golgi network. MSD affects the entire sulfatase family, at least seven members of which are lysosomal enzymes that are specifically involved in the degradation of sulfated glycosaminoglycans, sulfolipids or other sulfated molecules. The combined deficiencies of all sulfatases result from a defective post-translational modification by the ER-localized formylglycine-generating enzyme (FGE), which oxidizes a specific cysteine residue to formylglycine, the catalytic residue enabling a unique mechanism of sulfate ester hydrolysis. This review gives an update on the molecular bases of these enigmatic diseases, which have been challenging researchers since many decades and so far led to a number of surprising findings that give deeper insight into both the cell biology and the pathobiochemistry underlying these complex disorders. In case of MSD, considerable progress has been made in recent years towards an understanding of disease-causing FGE mutations. First approaches to link molecular parameters with clinical manifestation have been described and even therapeutical options have been addressed. Further. the discovery of FGE as an essential sulfatase activating enzyme has considerable impact on enzyme replacement or gene therapy of lysosomal storage disorders caused by single sulfatase deficiencies. (C) 2008 Elsevier B.V. All rights reserved.

First trimester prenatal diagnosis was offered to a couple at risk for having a child with I-cell disease (mucolipidosis II). The prenatal evaluation was based for the first time on examination of N-acetylglucosamine 1-phosphotransferase activity, deficiency of which is the primary biochemical defect in both I-cell disease and pseudo-Hurler polydystrophy (mucolipidosis III). Heterozygote levels of this enzyme activity were determined in chorionic villi obtained at 9 weeks of gestation, as well as in cultured trophoblasts derived from this specimen, and led to the diagnosis of an unaffected fetus. This procedure has advantages over that based on detection of abnormal intracellular-extracellular distribution of lysosomal enzyme activities, which is expressed only in homozygotes and fully expressed only in cell culture specimens.

Placentas were studied from three interrupted pregnancies of a mother whose first liveborn child had I-cell disease (mucolipidosis II). I-cell disease of the fetus was shown by investigation of the amniotic fluid, fetal cells and the aborted fetus in two pregnancies, but in the third case placenta was the only available product of conception. In every placenta extensive vacuolization of the syncytiotrophoblastic layer of the chorionic villi and chorionic mesenchymal cells was found. In electron microscopy the inclusions were identical to those of other tissues in I-cell disease. The importance of histological study of placenta in unexplained spontaneous abortions needs to be emphasized, since this may be the only way of detecing new cases of lysosomal storage diseases.

Normalization of multiple deficiency of intracellular lysosomal hydrolases in I-cell disease (ICD) fibroblasts by sucrose loading has been reported (Kato et al. (1982) J. Biol. Chem. 257, 7814). Further studies revealed that the effects of sucrose on the induction of hydrolases in seven ICD strains examined in this study were characteristic in each strain. The results may indicate that ICD strains can be classified into subgroups by the degree of enzymic induction. Moreover, this speculation seems to be supported by the normalization of electrophoretic patterns of beta-hexosaminidase in ICD fibroblasts after sucrose loading.

A severe form of I-cell disease (mucolipidosis II) can present in the newborn period as multiple fractures. The bone disease in these patients is believed to be due to hyperparathyroidism. We report a case where bone disease was present at birth but the parathyroid hormone levels were initially normal and did not increase until 37 d of age. Supplemention with vitamin D was needed to normalize the parathyroid hormone levels despite adequate intake of vitamin D, calcium and phosphorus. We suggest that in patients with I-cell disease, continued evaluation for hyperparathyroidism may be necessary despite initial normal parathyroid hormone levels.

Mucolipidosis II (Inclusion cell or I-cell disease) is an autosomal recessive lysosomal storage disorder clinically comparable to the mucopolysaccharidoses (MPS), characterized by progressive respiratory and neurologic deterioration. Sleep problems, especially obstructive sleep apnea (OSA) and disrupted sleep architecture, are observed in other lysosomal storage diseases but have not been described in mucolipidosis II. We report the progression of polysomnographic abnormalities in a child with mucolipidosis II, demonstrated by worsening sleep-related hypoventilation, OSA, and sleep state fragmentation despite advancing PAP therapy. Background slowing and reduction in spindle activity on limited EEG may reflect progressive CNS disease affecting thalamic neurons.

I-cell disease is a rare autorecessive metabolic disorder that is classified as one of the lysosomal storage diseases. Gingival enlargement is a representative oral manifestation of patients with I-cell disease. This report describes a case with a satisfactory prognosis after gingivectomy for gingival enlargement accompanying I-cell disease in a 2-year-old boy. The chief complaints were both eating disorders and night terrors accompanied by gingival enlargement of both the maxillary and mandibular alveolar gingivae, especially in the region of the first deciduous molars. Although it was supposed that there were various hazards associated with gingivectomy caused by aortic incompetence, sigmoidal spinal curvature and hypertrophy of the laryngopharynx, gingivectomy with an internal bevel incision was performed under general anesthesia to improve the chief complaints. A piece of the enlarged gingivae dissected during the operation was examined histopathologically, and the histopathological diagnosis was gingival hyperplasia. The patient's signs and symptoms of the eating disorders and night terrors have improved since the gingivectomy operation. Recurrence of the gingival enlargement has not been identified up to 18 months after the surgery. It is therefore concluded that gingivectomy for gingival enlargement accompanying I-cell disease was effective for this 2-year-old boy.

Drug-induced gingival overgrowth, the chronic side effect of calcium antagonists, is frequently seen due to the increase in patients with hypertension, although the etiology of the disease is largely unknown. I-cell disease, which accompanies gingival overgrowth, is characterized by a deficiency in UDP-N-acetyl-glucosamine and is classified as one of the lysosomal storage diseases. Here, we hypothesized that a common mechanism may underlie the etiology of gingival overgrowth seen in patients treated with calcium antagonist and in patients with I-cell disease. A calcium antagonist, nifedipine, specifically suppressed cathepsin-L activity and mRNA expression, but not that of cathepsin-B in cultured gingival fibroblasts. The activity of cathepsin-L was suppressed up to 50% at 24 hours after treatment of the cells with the reagent. The selective suppression of cathepsin-L activity appeared not to be dependent on Ca 2+ , since treatment of the cells with thapsigargin suppressed both cathepsin-B and -L activity. Mice deficient in the cathepsin-L gene manifested enlarged gingivae. Histological observation of the gingivae demonstrated typical features of acanthosis, a phenotype very similar to that of experimentally induced gingival overgrowth. Since cathepsin-L deficiency was reported to be associated with thickening of the skin, impaired cathepsin-L activity may play a key role in the establishment of skin and gingival abnormalities seen in I-cell disease. In addition, reduced cathepsin-L activity may play an important role in inducing drug-induced gingival overgrowth.

Mucolipidosis type II (MLII), or I-cell disease, is a rare but severe disorder affecting localization of enzymes to the lysosome, generally resulting in death before the 10th birthday. Although hematopoietic stem cell transplantation (HSCT) has been used to successfully treat some lysosomal storage diseases, only 2 cases have been reported on the use of HSCT to treat MLII. For the first time, we describe the combined international experience in the use of HSCT for MLII in 22 patients. Although 95% of the patients engrafted, overall survival was low, with only 6 patients (27%) alive at last follow-up. The most common cause of death post-transplant was cardiovascular complications, most likely due to disease progression. Survivors were globally delayed in development and often required complex medical support, such as gastrostomy tubes for nutrition and tracheostomy with mechanical ventilation. Although HSCT has demonstrated efficacy in treating some lysosomal storage disorders, the neurologic outcome and survival for patents with MLII were poor. Therefore, new medical and cellular therapies should be sought for these patients.

Background: Clinical differentiation among mucopolysaccharidosis, oligosaccharidosis, and mucolipidosis II and III is difficult. We describe methods for the assay of 8 lysosomal enzymes in dried blood spots on filter paper that allow screening for 12 lysosomal storage diseases that present with a Hurler-like phenotype. Methods: To test tubes containing 3-mm blood spots, we added elution liquid and fluorescent or radioactive substrate solution. After incubation at 37 °C, the reaction was terminated by the addition of a stop buffer. The amount of hydrolyzed product was compared with a calibrator to allow the quantification of enzyme activity. Sample stability was studied during storage for 21 days and during shipment of samples. We measured enzyme activities in 85 healthy controls (35 newborn, 50 adult), 57 patients suffering from 11 lysosomal storage diseases, and 46 obligate carriers. Results: Intra- and interassay CVs were Conclusions: The described methodology distinguishes between patients and controls with samples that are sufficiently stable to be mailed to the testing laboratory.

Six antibiotics, pefloxacin (Peflacine), fosfomycin (Fosfocine), teicoplanin (Targocid), vancomycin (Vancocine), ceftazidime (Fortum), piperacillin (Piperilline), that may be used as a systematic coverage during bone marrow transplantation have been tested on dermal fibroblasts of one control subject and two I-cell disease patients, along with five subcultures, corresponding to 5 weeks of culture. The possible toxicity of these molecules was assessed. The evaluation of lysosomal enzyme sphingomyelinase activity, detection of free intracellular cholesterol and the light- and electron-microscopic examination of treated cells were used as measures of metabolic interference and cytotoxicity. Our study shows that despite a lack of any metabolic sign of interference (no modification in enzyme activity, no increase in free intracellular cholesterol), all the antibiotics tested induced a cytotoxic effect which was notably amplified in the I-cell populations. This may be due to the lysosomal lipid storage of these cells which modifies the relationship between the antibiotic and the cell by inducing a different kind of lipid-antibiotic interference.

Mutations in the gene encoding a recently described lysosomal enzyme, palmitoyl-protein thioesterase (PPT), have recently been shown to result in the neurodegenerative disorder, infantile neuronal ceroid lipofuscinosis (INCL). Reduced palmitoyl-protein thioesterase enzyme has been demonstrated previously in INCL brain and immortalized lymphoblasts. In the current paper, we demonstrate that: (1) PPT can be detected by immunoblotting and enzyme activity assays in normal human skin fibroblasts; (2) INCL fibroblasts are deficient in PPT activity; (3) I-cell disease fibroblasts show markedly reduced intracellular levels of PPT but markedly increased levels of PPT in cell culture medium. These data establish that PPT is transported to lysosomes via the lysosomal enzyme:lysosomal enzyme receptor phosphomannosyl recognition system under normal physiological conditions and provide the basis for a useful clinical assay for INCL.

A 7-month-old female cat was seen for abnormal facial features and abnormality of gait. Facial dysmorphism, large paws in relation to body size, dysostosis multiplex, and poor growth were noted, and mucopolysaccharidosis was suspected. A negative urine test for sulfated glycosaminoglycans and extreme stiffness of skin indicated a mucolipidosis hitherto unknown in animals. Deficiency of UDP-N-acetylglucosamine: lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase, EC 2.7.8.17) activity was demonstrated in leukocytes and cultured fibroblasts, which had the appearance of inclusion cells (I-cells). Activities of a set of lysosomal hydrolases were abnormally low in fibroblasts and excessive in blood plasma. Postmortem morphology revealed lysosomal inclusions predominantly in fibroblasts but also in endothelial cells and chondrocytes, i.e., in cells of mesenchymal origin. Storage lysosomes contained oligosaccharides, mucopolysaccharides, and lipids. Tissues most affected were bones, cartilage, skin, and other connective tissues such as those in heart valves, aortic wall, and vocal cords. Parenchymal cells of liver and kidney were unaffected, as was skeletal muscle. Only a few of the cerebral cortical neurons had lipid inclusions; in sciatic nerve some axons were affected, but other peripheral nerves were normal. There were striking clinical, biochemical, and morphologic similarities between the disorder in this cat and the human I-cell disease.

A 28-year-old G3 P1 SAB1 female with no prior health concerns was found to have a foetus with short femurs on prenatal ultrasound following an abnormal maternal serum screen result. Fluid obtained by amniocentesis revealed an elevated α-fetoprotein level with absence of an acetylcholinesterase band and normal male karyotype (46,XY). Follow-up ultrasound 3 weeks later again demonstrated short femur lengths, but no other abnormalities. At birth, the child was noted to have multiple dysmorphic features, including short humeri and femurs, coarse facial features, retrognathia and yellowish hypertrophic gums in addition to hyperbilirubinaemia and thrombocytopenia. Radiological studies demonstrated bony demineralization with profound diaphyseal cloaking in the long bones. Genetic testing diagnosed I-cell disease.

Protein catabolism in fibroblasts cultured from the skin of normal individuals and of patients with mucolipidosis II (I-cell disease) and several other lysosomal storage diseases was examined by metabolic labelling with [3H]leucine and following the fate of radioactive proteins in pulse-chase experiments. In mucolipidosis II cells, overall protein degradative rates were found to be distinctly lower than in normal control cells. To distinguish lysosomal from non-lysosomal degradation, labelling experiments were carried out in the presence and absence of 10 mM NH4Cl, an inhibitor of lysosomal function. It was found that mucolipidosis II fibroblasts exhibited a markedly reduced rate of lysosomal protein degradation, whereas the rate of nonlysosomal degradation appeared normal. Serum and amino acid starvation led to a marked increase in lysosomal protein degradation in normal cells, but had only a minimal effect on that in mucolipidosis II fibroblasts. The specific activities of cathepsins B, H and L were profoundly diminished in all mucolipidosis II cell lines tested. Lysosomal protein degradation in a mucolipidosis III cell line was impaired to a similar degree as in mucolipidosis II cells, whereas it was decreased to a lesser extent in fibroblasts from patients with mucopolysaccharidoses I and VI, galactosialidosis and GM1-gangliosidosis. We conclude that fibroblasts from patients with mucolipidosis II and III have a severely compromised capacity for endogenous lysosomal protein degradation that appears to result from multiple cathepsin deficiency. This lysosomal defect is likely to have pathophysiological consequences.

Mucolipidosis (ML) II alpha/beta and III alpha/beta are autosomal recessive diseases caused by a deficiency of alpha and/or beta subunits of the enzyme N-acetylglucosamine-1-phosphotransferase, which is encoded by the GNPTAB gene. We analyzed the GNPTAB gene in 25 ML II and 15 ML III Japanese patients. In most ML II patients, the clinical conditions 'stand alone', 'walk without support' and 'speak single words' were impaired; however, the frequency of 'heart murmur', 'inguinal hernia' and 'hepatomegaly and/or splenomegaly' did not differ between ML II and III patients. We detected mutations in GNPTAB in 73 of 80 alleles. Fourteen new mutations were c.914_915insA, c.2089_2090insC, c.2427delC, c.2544delA, c.2693delA, c.3310delG, c.3388_3389insC+c.3392CT, c.3428_3429insA, c.3741_3744delAGAA, p.R334L, p.F374L, p.H956Y, p.N1153S and duplication of exon 2. Previously reported mutations were p.Q104X, p.W894X, p.R1189X and c.2715+1GA causing skipping of exon 13. Homozygotes or compound heterozygotes of nonsense and frameshift mutations contributed to the severe phenotype. p.F374L, p.N1153S and splicing mutations contributed to the attenuated phenotype, although coupled with nonsense mutation. These results show the effective molecular diagnosis of ML II and III and also provide phenotypic prediction. This is the first and comprehensive report of molecular analysis for ML patients of Japanese origin.

Mucolipidosis (ML) II (I-cell disease) is a lysosomal storage disorder caused by a deficiency of UDP-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase. MLII is an autosomal recessive disease with a carrier rate estimated at 1/39 in Saguenay-Lac-Saint-Jean (SLSJ) (Quebec, Canada), which is the highest frequency documented worldwide. To identify the causing mutation, we sequenced GNPTAB exons in 27 parents of 16 MLII-deceased children from the SLSJ region as obligatory and potential carriers. We also performed a genealogical reconstruction for each parent to evaluate consanguinity levels and genetic contribution of ancestors. Our goal was to identify which parameters could explain the high MLII frequency observed in the SLSJ population. A single mutation (c.3503_3504delTC) was found in all obligatory carriers. In addition, 11 apparent polymorphisms were identified. The mutation was not detected in genomic DNA of 50 unrelated controls. Genealogical data show six founders (three couples) with a higher probability of having introduced the mutation in the population. The frequency of the mutation was increased as a consequence of this founder effect and of the resulting population structure. We suggest that c.3503_3504delTC is the allele causing MLII in the SLSJ population, and its high carrier rate is most likely explained by a founder effect.