Hearing impairment as an early sign of alpha‐mannosidosis in children with a mild phenotype: Report of seven new cases

Alpha‐mannosidosis (AM) is a very rare (prevalence: 1/500000 births) autosomal recessive lysosomal storage disorder. It is characterized by multi‐systemic involvement associated with progressive intellectual disability, hearing loss, skeletal anomalies, and coarse facial features. The spectrum is wide, from very severe and lethal to a milder phenotype that usually progresses slowly. AM is caused by a deficiency of lysosomal alpha‐mannosidase. A diagnosis can be established by measuring the activity of lysosomal alpha‐mannosidase in leucocytes and screening for abnormal urinary excretion of mannose‐rich oligosaccharides. Genetic confirmation is obtained with the identification of MAN2B1 mutations. Enzyme replacement therapy (LAMZEDE^R) was approved for use in Europe in August 2018. Here, we describe seven individuals from four families, diagnosed at 3–23 years of age, and who were referred to a clinical geneticist for etiologic exploration of syndromic hearing loss, associated with moderate learning disabilities. Exome sequencing had been used to establish the molecular diagnosis in five cases, including a two‐sibling pair. In the remaining two patients, the diagnosis was obtained with screening of urinary oligosaccharides excretion and the association of deafness and hypotonia. These observations emphasize that the clinical diagnosis of AM can be challenging, and that it is likely an underdiagnosed rare cause of syndromic hearing loss. Exome sequencing can contribute significantly to the early diagnosis of these nonspecific mild phenotypes, with advantages for treatment and management.     

Mannosidosis in two brothers: prolonged survival in the severe phenotype

Two cases of mannosidosis are reported in brothers, one aged 41 years at death, the other aged 40 years and still alive. These patients are the oldest reported in the literature. Prolonged survival has previously been associated with the milder Type II phenotype. In addition to the characteristic clinical and radiological features of mannosidosis, both had severe joint destruction, which may be related to abnormal lysosomal enzymes in cartilage. The activity of acidic a-mannosidase was markedly reduced in plasma, leucocytes and fibroblasts, and the altered kinetic and physical properties are described.     

Alpha-mannosidosis: analysis of urinary oligosaccharides with high performance liquid chromatography and diagnosis of a case with unusually mild presentation

Mannose containing oligosaccharides (OS) excreted in the urine of patients with alpha-mannosidosis have been analyzed with high performance liquid chromatography (HPLC). The HPLC method provides a highly sensitive assay for detection of the urinary oligosaccharides and was employed for diagnosis of a fifteen-year-old female with an unusually mild presentation of the disease. Dysostosis multiplex and coarse facies were absent; mental impairment was particularly mild. The elution profile of the urinary OS from this patient and two, more severely affected, patients with mannosidosis were nearly identical, containing nine major OS fractions. The concentrations of the OS were eight fold lower in our patient hut, when calculated relative to creatinine, the levels of the urinary OS of all patients were similar.     

Co-occurrence of three different mutations in the bilirubin UDP-glucuronosyltransferase gene in a Chinese family with Crigler-Najjar syndrome type I and Gilbert's syndrome

Crigler-Najjar syndrome type I is a severe form of hereditary unconjugated hyperbilirubinemia and is caused by homozygous or compound heterozygous mutations of the bilirubin UDP-glucuronosyltransferase gene (UGT1A1). We analyzed the bilirubin UDP-glucuronosyltransferase gene in a female Chinese patient with Crigler-Najjar syndrome type I. Relatives of the patient were also analyzed. The patient was homozygous for a nonsense mutation of R341X. The patient's father, sister and brother, all diagnosed with Gilbert's syndrome, were compound heterozygotes of R341X, P229Q, and an insertion mutation of the TATA box [A(TA)7TAA]. Heterozygotes of nonsense mutations (Q331X and C280X) in our previous study had either Crigler-Najjar syndrome type II or Gilbert's syndrome, but heterozygotes of R341X (mother and grandmothers) were normal. An in vitro expression study of homozygous and heterozygous models of R341X showed 0 and 58%, respectively, of normal enzyme activity. Therefore, the present results indicate that carriers of the nonsense mutation could be normal for plasma bilirubin concentration, Gilbert's syndrome and Crigler-Najjar syndrome type II. The results also suggest the importance of the accumulation of prevalent or polymorphic mutation in the etiology of Gilbert's syndrome and Crigler-Najjar syndrome type II.     

Type I and type II interferons: differential antiviral actions in transformed cells

In transformed mouse embryo cells, type II interferon had much less antiviral activity than type I interferon. In non-transformed cells, the two interferons had similar high activity, Reversal of the phenotype of Moloney sarcoma virus (MSV) transformed cells by sodium butyrate restored their sensitivity to the antiviral action of type II interferon. Additional evidence for a role of the cytoskeletal network in the action of type II interferon is that its antiviral effect is reduced by cytochalasin B, colchicine or vinblastine. MSV-transformed cells, selected for their resistance to the antiviral action of type I interferon, were sensitive to type II interferon. These differences in the effects of type I and II interferon on transformed cells are at present unexplained, but suggest that they have at least partially separate mechanisms of action.     

The mucolipidoses: Identification by abnormal electrophoretic patterns of lysosomal hydrolases

The human mucolipidoses (ML) are characterized by abnormal activities and abnormal electrophoretic patterns of fibroblast lysosomal hydrolases. These altered mobility patterns can be used to confirm the clinical diagnosis of the four mucolipidoses. The mobility patterns of one nonlysosomal and seven lysosomal enzymes were tested in fibroblasts from two ML I (sialidosis type 2, infantile), fifteen ML II (I-cell disease), eight ML III (pseudohurler poly-dystrophy), and one ML IV patients. A single sialidosis type 2, juvenile, line was also examined. Characteristic mobility patterns were found which identify each of the four mucolipidoses. Both the ML I and sialidosis type 2 juvenile lines displayed anodal mobility patterns, but distinct differences between the two disorders were observed. Lysosomal hydrolases from ML II lines demonstrated reduced activities or had altered mobilities. Differing electrophoretic patterns demonstrated the presence of at least two groups within the clinical phenotype diagnosed as ML II, indicating heterogeneity. The ML III lines showed normal electrophoretic patterns for most lysosomal hydrolases. The ML IV line expressed normal mobilities for every enzyme studied, with a single exception. The electrophoretic patterns of only β-hexosaminidase, acid phosphatase-2, α-galactosidase, and esterase A₄ were sufficient to identify and distinguish the different mucolipidosis types. Electrophoretic variation was also seen in liver but not kidney extracts from three ML II patients. β-Hexosaminidase and α-mannosidase B secreted into the medium by ML II and ML III fibroblasts had mobility patterns different from normal and from their intracellular patterns. These data suggest that the mucolipidoses are genetically distinct with heterogeneity within them.     

Changes of serum hexosaminidase for the presumptive diagnosis of type I Gaucher disease in Tay-Sachs carrier screening

Although reduced acid β-glucosidase activity appears to be the primary enzyme defect in type I Gaucher disease, patients with this disorder also have marked elevation of serum acid phosphatase and β-hexosaminidase activities but with a normal level of lactic dehydrogenase activity. Moreover, there is a characteristic alteration in the hexosaminidase isozyme distribution with a striking increase in hexosaminidase B. Since these changes appear to be consistent and unlike those associated with other disorders or the hormonally induced alterations associated with pregnancy, routine serum testing for the Tay-Sachs carrier state may offer a useful approach for the presumptive diagnosis and screening for Gaucher disease. Unlike the changes in affected homozygotes, there are no characterisitic alterations of acid phosphatase or hexosaminidase in heterozygotes for Gaucher disease.     

Alpha‐mannosidosis: characterization of CNS pathology and correlation between CNS pathology and cognitive function

Alpha‐mannosidosis (AM) (OMIM 248500) is a rare lysosomal storage disease. The understanding of the central nervous system (CNS) pathology is limited. This study is the first describing the CNS pathology and the correlation between the CNS pathology and intellectual disabilities in human AM. Thirty‐four patients, aged 6–35 years, with AM were included. Data from 13 healthy controls were included in the analysis of the magnetic resonance spectroscopy (MRS). Measurements of CNS neurodegeneration biomarkers in cerebrospinal fluid (CSF), CSF‐oligosaccharides, and performance of cerebral magnetic resonance imaging (MRI) and MRS were carried out. On MRI, 5 of 10 patients had occipital white matter (WM) signal abnormalities, and 6 of 10 patients had age‐inappropriate myelination. MRS demonstrated significantly elevated mannose complex in gray matter and WM. We found elevated concentrations of tau‐protein, glial fibrillary acidic protein and neurofilament light protein in 97 patients, 74% and 41% of CSF samples, respectively. A negative correlation between CSF‐biomarkers and cognitive function and CSF‐oligosaccharides and cognitive function was found. The combination of MRS/MRI changes, elevated concentrations of CSF‐biomarkers and CSF‐oligosaccharides suggests gliosis and reduced myelination, as part of the CNS pathology in AM. Our data demonstrate early neuropathological changes, which may be taken into consideration when planning initiation of treatment.     

Heterozygous cystinuria and urinary lithiasis

Cystinuria is a recessively inherited transport disorder, with at least three mutant alleles (I, II, and III) demonstrable. I/I, II/II, and III/III homozygotes and I/II, I/III, and II/III compound heterozygotes (cystinuric patients) have high urinary concentrations of cystine, lysine, arginine, and ornithine and frequently form cystine stones. +/I heterozygotes (nondetectable) are phenotypically normal, whereas +/II and +/III heterozygotes (detectable) show variable increases in urinary cystine and lysine concentration and at times increases in urinary arginine levels. The objectives of the present study were to determine the frequency of +/II heterozygotes among stone-forming and nonstone-forming individuals from the same region of Brazil and to evaluate the possible relationship between heterozygous cystinuria and urinary lithiasis. When urine samples from 5,150 individuals (5,000 nonstone-forming individuals and 150 stone-forming individuals) were screened by the qualitative cyanide-nitroprusside cystine test, by thin-layer amino acid chromatography, and by quantitative amino acid determination by ion-exchange chromatography, 32 +/II or +/III heterozygotes (26 nonstone-forming and six stone-forming individuals) were detected. The frequency of detectable heterozygotes among the stone-forming individuals (1:25) was significantly higher than that among nonstone-forming individuals (1:104), which provides additional evidence that heterozygosity for +/II and +/III cystinuria is a risk factor in the formation of urinary stones. No significant difference was detected in urinary cystine concentration or in terms of the various characteristics of urolithiasis when stone-forming heterozygotes were compared to nonstone-forming heterozygotes. These data suggest that the tendency towards stone-forming among heterozygotes is probably owing to a complex and multifactorial mechanism.     

An α1 II Gly913 to Cys substitution prevents the matrix incorporation of type II collagen which is replaced with type I and III collagens in cartilage from a patient with hypochondrogenesis

A heterozygous mutation in the COL2A1 gene was identified in a patient with hypochondrogenesis. The mutation was a single nucleotide transition of G3285T that resulted in an amino acid substitution of Cys for Gly⁹¹³ in the α1(II) chain of type II collagen. This amino acid change disrupted the obligatory Gly-X-Y triplet motif required for the normal formation of a stable collagen triple helix and prevented the deposition of type II collagen into the proposita's cartilage, which contained predominantly type I and III collagens and minor amounts of type XI collagen. Biosynthetic analysis of collagens produced and secreted by the patient's chondrocytes cultured in alginate beads was consistent with the in vivo matrix composition, demonstrating that the main products were type I and III collagens, along with type XI collagen. The synthesis of the cartilage-specific type XI collagen at similar levels to controls indicated that the isolated cartilage cells had re-differentiated to the chondrocyte phenotype. The chondrocytes also produced small amounts of type II collagen, but this was post-translationally overmodified and not secreted. These data further delineate the biochemical and phenotypic consequences of mutations in the COL2A1 gene and suggest that cartilage formation and bone development can take place in the absence of type II collagen. © 1996 Wiley-Liss, Inc.     

Diagnostic strategy of mucopolysaccharidosis type I in Tunisia

A Tunisian patient affected by mucopolysaccharidosis (MPS) was investigated for a biological analysis (quantitative and qualitative glycosaminoglycans (GAG) screening). We have also done an enzymatic determination of alpha-L-iduronidase activity (IDUA). The most common mutation (p.Gln 70 X, p.Trp 402X and p.Pro 533 Arg) were researched by an enzymatic restriction and sequencing of the IDUA gene. Enzymatic and urinary diagnostics suggested a MPS I phenotype. The patient investigated had the mutation p.Pro 533 Arg in the homozygous status, whereas his parents were heterozygous for this mutation.     

A family with pseudodeficiency of acid α-glucosidase

A unique family is presented which consists of a patient with the juvenile muscular dystrophy form of glycogenosis type II and four healthy individuals, both parents and sisters, with low acid alpha-glucosidase activity. It was almost impossible to distinguish the homozygote from the heterozygous members by lymphocyte assay alone. In cultured skin fibroblasts, acid alpha-glucosidase activity measured with a synthetic substrate was less than 1% of the normal mean value in the patient and about 15% in the parents. The activity toward glycogen was not detectable in the patient and was about 30% of the normal mean value in the parents. These values are also lower than expected in heterozygotes. To explain these results properly, a new mutant allele of acid alpha-glucosidase is proposed. Both parents could be compound heterozygotes for the pseudodeficiency allele and the juvenile form of glycogenosis type II allele.     

Achondrogenesis type IB (Fraccaro): Study of collagen in the tissue and in chondrocytes cultured in agarose

A lethal chondrodysplasia characterized by extreme micromelia was diagnosed by ultrasound examination in two sibs whose nonconsanguineous parents were healthy. Radiographic and histopathologic data indicated that the two foetuses (18 and 21 weeks old) had achondrogenesis type IB (Fraccaro). Quantitation of total collagen extractable from dried cartilage samples demonstrated a 50% decrease when compared to an age-related control. This decrease was essentially related to type II collagen. Nevertheless, the α chains and the CB peptides of type II collagen had a normal electrophoretic mobility. A significant amount of collagen type I was also detected. The electrophoretic pattern of collagens type IX and XI did not differ significantly from control sample. The extracellular matrix elaborated by patient chondrocytes cultured in agarose for 10–12 days, contained less collagen type II than normal cells. Labelling with ¹⁴C-proline of cultured cells showed the presence of pro-collagen and type II collagen chains with a normal electrophoretic mobility, but an α2(I) chain was detectable in the patient material, indicating the presence of collagen type I which supported the tissue findings. The significance of the type II collagen reduction in the patient's cartilage is unclear but it is unlikely to be the primary defect in achondrogenesis type I. © 1994 Wiley-Liss, Inc.     

Critical role of the endogenous interferon ligand–receptors in type I and type II interferons response

Separate ligand–receptor paradigms are commonly used for each type of interferon (IFN). However, accumulating evidence suggests that type I and type II IFNs may not be restricted to independent pathways. Using different cell types deficient in IFNAR1, IFNAR2, IFNGR1, IFNGR2 and IFN‐γ, we evaluated the contribution of each element of the IFN system to the activity of type I and type II IFNs. We show that deficiency in IFNAR1 or IFNAR2 is associated with impairment of type II IFN activity. This impairment, presumably resulting from the disruption of the ligand–receptor complex, is obtained in all cell types tested. However, deficiency of IFNGR1, IFNGR2 or IFN‐γ was associated with an impairment of type I IFN activity in spleen cells only, correlating with the constitutive expression of type II IFN (IFN‐γ) observed on those cells. Therefore, in vitro the constitutive expression of both the receptors and the ligands of type I or type II IFN is critical for the enhancement of the IFN activity. Any IFN deficiency can totally or partially impair IFN activity, suggesting the importance of type I and type II IFN interactions. Taken together, our results suggest that type I and type II IFNs may regulate biological activities through distinct as well as common IFN receptor complexes.     

Isozyme pattern of leukocyte α-d-mannosidase in patients with mannosidosis

The isozyme patterns of leukocyte -d-mannosidase in two sisters with mannosidosis, their parents and a patient with trisomy 19 were studied. The isozyme pattern of liver mannosidase of a normal subject was also studied. In the patients with mannosidosis the neutral isozyme (isozyme C or fraction C) was present, but the acidic isozymes (isozyme A and B or fraction A and B) were not detectable. In their parents the activity of the acidic isozymes was one-third of the normal activity. These findings suggest that the patients are homozygous and their parents are heterozygous in terms of deficiency of acidic isozymes. In the patients with trisomy 19, the activity of -d-mannosidase was 4.9 times the upper limit of the normal value, while the levels of other lysozomal enzymes were normal. This increase was mainly due to increases of the A and B isozymes of mannosidase. This finding suggests that the gene encoding acidic isozymes, but not that encoding the neutral isozyme, is located on chromosome 19. The isozyme pattern of -d-mannosidase differed in different tissues of normal subjects, and the difference in severity of lesions in different organs of the patients with mannosidosis could be explained by differences in the isozyme patterns of the enzyme in these organs.     

Urinary exoglycosidases,reference values in healthy children

Purpose

The purpose of the study was to determine the effect of age on lysosomal exoglycosidase activities: α-fucosidase, β-galactosidase, β-glucuronidase and α-mannosidase in healthy children and adolescents.

Atypical skeletal changes in otopalatodigital syndrome type II: Phenotypic overlap among otopalatodigital syndrome type II,boomerang dysplasia,atelosteogenesis type I and type III,and lethal male phenotype of Melnick-Needles syndrome

We report on 2 cases of otopalatodigital syndrome type II (OPD II) with atypical skeletal changes, overlapping those of boomerang dysplasia, atelosteogenesis type I (AO I) and type III (AO III), and the lethal male phenotype of Melnick-Needles syndrome. One patient exhibited strikingly broad, bowed femora, which resembled those of boomerang dysplasia. The other patient possessed conspicuous undertubulation of the long bones, defective ossification of the spine, and severe undermineralization of the calvaria, which may have caused diagnostic confusion with AO I, AO III, and the lethal male phenotype of Melnick-Needles syndrome. OPD II is transmitted as an X-linked recessive trait, whereas AO I, AO III, and boomerang dysplasia are considered to result from a new dominant mutation, and Melnick-Needles syndrome is inherited as an X-linked dominant trait. Accordingly, differential diagnosis is mandatory to provide the affected families with adequate genetic counseling. Awareness of these skeletal changes in OPD II will prevent the misdiagnosis of this entity as other disorders. Furthermore, the phenotypic overlap among these disorders may expand the entities that constitute the OPD-Larsen dysplasia family proposed by Spranger [1985]. Am. J. Med. Genet. 73:132–138, 1997. © 1997 Wiley-Liss, Inc.     

Are MPS II heterozygotes actually asymptomatic? A study based on clinical and biochemical data,X‐inactivation analysis and imaging evaluations

For some X-linked disorders the expressivity and penetrance in females are almost similar to those ones found in males. For mucopolysaccharidosis type II (MPS II), there are no studies in the literature trying to identify subtle signs and symptoms of this disease in heterozygotes. The objective of this study was to compare heterozygotes and non-heterozygotes for MPS II, in order to test the hypothesis that heterozygotes may present subtle manifestations of the disease. In this observational and transversal study we collected data on 40 Brazilian women with a positive familial history for MPS II that included clinical and physical exam, karyotype, pattern of X-inactivation, iduronate-2-sulfatase (IDS) activity in leukocytes and plasma, urinary glycosaminoglycans levels, computerized tomography scans (CT) of abdomen and spine, and brain magnetic resonance imaging. The Results showed the following: According to DNA analysis, 22 women were classified as heterozygote and 18 as non-heterozygotes. We did not find any abnormality on physical examination, karyotype, or spine CT. Also the pattern of X-inactivation was not different between the groups. Applying the Bonferroni's correction, both groups were found to differ only in relation to IDS activity in plasma and in leukocyte, which were lower in heterozygotes. In our investigation we did not find any evidence of subtle clinical manifestations of MPS II in heterozygotes. Our findings suggest there is no relation between the absence of clinical signs in these women and the occurrence of a favorable skewing pattern of X-inactivation.