Sialidosis type 2 (acid neuraminidase deficiency): clinical and biochemical features of a further case

A further patient with a presumed primary deficiency of sialidase N-acetylneuraminic acid hydrolase EC 3.2.1.18) is described. Clinically the patient falls into the sialidosis type 2 category of the recent classification of Lowden & O'Brien (1979), i.e. he manifests coarse facies, mental retardation and skeletal changes of dysostosis multiplex as well as myoclonus and a cherry-red spot at the macula. Sialidase activity in fibroblasts was 4% of control values using a methylumbelliferone substrate. The father of the patient was found to have 50% activity. Abnormal amounts of sialyloligosaccharides were found in the urine. The electrophoretic mobility of known glycosylated enzymes and proteins was found to be altered (more anodal than usual), but could be corrected by incubation of the cell extracts with bacterial neuraminidase. The relationship of the present patient to the Lowden & O'Brien classification is discussed.     

Combined sialidase (neuraminidase) and β-galactosidase deficiency. Clinical, morphological and enzymological observations in a patient

A patient with combined deficiency of sialidase and beta-galactosidase is described. This now 39-year-old man, who is of Japanese origin, showed gradually progressive clinical features from the age of six years. Many of these features are commonly found in sialidosis type 2 or in GM1-gangliosidosis. Both sialidase and beta-galactosidase activities were deficient in leucocytes and cultured fibroblasts. Leucocytes of his mother showed activities of both enzymes in the lower limit of the control range. Morphologically, the pattern of storage products in a skin biopsy resembled in many respects that seen in GM1-gangliosidosis. Moreover, storage products which could be typical of sialidosis were also observed. Since the patient showed angiokeratomata, the morphological findings were compared with those specific to Fabry's disease, but no similarities were found. An enzymological diagnosis of the disease is most reliable on cultured fibroblasts, discriminating it from sialidosis type 2 and GM1-gangliosidosis. In view of recent findings, leucocytes seem to be less suitable for the establishment of the diagnosis galactosialidosis.     

Sialidosis: delineation of subtypes by neuraminidase assay

A sensitive assay for acid neuraminidase using 4–methylumbelliferyl-α-D-N-acetylneura-mink acid is described. In skin fibroblasts, patients with sialidosis Types 1 and 2 have severe deficiencies of neuraminidase activity compared with controls. Patients with Type 1 sialidosis have activities which are 10 times higher than those with Type 2 sialidosis, in keeping with their milder clinical involvement. Two Italian patients with Type I sialidosis had a K_m which was one-sixth normal; the other patients had a K_m in the normal range.     

Prenatal diagnosis of congenital sialidosis

Sasagasako N, Miyahara S, Saito N, Shinnoh N, Kobayashi T, Goto I. Prenatal diagnosis of congenital sialidosis.
Clin Genet 1993: 44: 8–11. © Munksgaard, 1993
A case of prenatally diagnosed congenital sialidosis is described in a 21-week-old male fetus, which was the fifth product of non-consanguineous parents. The proband, the second product, was diagnosed as having sialidosis by the enzyme assay in peripheral leukocytes after birth. At the 17th week of pregnancy, the fetus at risk was proven to have isolated sialidase deficiency after analyzing a sample of the cultured amniotic fluid cells. There were many cytoplasmic vacuoles and increased amounts of sialyloligosaccharides in the tissue of the aborted fetus, while the amount and the pattern of gangliosides in the central nervous system were normal.     

Molecular pathology of NEU1 gene in sialidosis

Lysosomal sialidase (EC 3.2.1.18) has a dual physiological function; it participates in intralysosomal catabolism of sialylated glycoconjugates and is involved in cellular immune response. Mutations in the sialidase gene NEU1, located on chromosome 6p21.3, result in autosomal recessive disorder, sialidosis, which is characterized by the progressive lysosomal storage of sialylated glycopeptides and oligosaccharides. Sialidosis type I is a milder, late-onset, normosomatic form of the disorder. Type I patients develop visual defects, myoclonus syndrome, cherry-red macular spots, ataxia, hyperreflexia, and seizures. The severe early-onset form, sialidosis type II, is also associated with dysostosis multiplex, Hurler-like phenotype, mental retardation, and hepatosplenomegaly. We summarize information on the 34 unique mutations determined so far in the sialidase gene, including four novel missense and one novel nonsense mutations found in two Czech and two French sialidosis patients. The analysis of sialidase mutations in sialidosis revealed considerable molecular heterogeneity, reflecting the diversity of clinical phenotypes that make molecular diagnosis difficult. The majority of sialidosis patients have had missense mutations, many of which have been expressed; their effects on activity, stability, intracellular localization, and supramolecular organization of sialidase were studied. A structural model of sialidase allowed us to localize mutations in the sialidase molecule and to predict their impact on the tertiary structure and biochemical properties of the enzyme.     

The cherry red spot—myoclonus syndrome: A newly recognized inherited lysosomal storage disease due to acid neuraminidase deficiency

A newly discovered lysosomal storage disorder, apparently transmitted as an autosomal recessive trait, presents with cherry red spots in childhood, progressive debilitating myoclonus, insidious visual loss, and normal intelligence. Somatic and bony abnormalities are not evident clinically. Neuronal lipidosis and vacuolated Kuppfer cells are found upon tissue examination. The diagnosis can be most easily confirmed by chromatographic screening for urinary sialyloligosaccharides. The primary enzyme defect is a deficiency of an acid neuraminidase isoenzyme which cleaves sialyloligosaccharides. I discuss here the clinical phenotype in four patients, the chemical abnormality, the pathogenesis, the enzyme defect and the molecular genetics of this disorder.     

Mucopolysaccharidosis type VII (β-glucuronidase deficiency): a report of a new case and a survey of those in the literature

A new case of mucopolysaccharidosis type VII ( β -glucuronidase deficiency) is described which presented with relatively mild clinical symptoms including disproportionate dwarfism, sternal protrusion, slight hepatomegaly and a small hernia. Facial features were not coarse and no neurological abnormalities were present. Urinary analysis revealed an increased excretion of chondroitin 4– and 6– sulphates. β- glucuronidase activity was virtually absent in serum and cultured fibroblasts. The results, together with a clinical follow-up of a previous case, are compared with the few cases described in the literature.     

Five novel mutations in the lysosomal sialidase gene (NEU1) in type II sialidosis patients and assessment of their impact on enzyme activity and intracellular targeting using adenovirus-mediated expression

Sialidosis is an autosomal recessive disease resulting from a deficiency of lysosomal sialidase. Type II sialidosis is a rare disease characterized clinically by hydrops fetalis, hepatosplenomegaly, and severe psychomotor retardation. Genomic DNA from four unrelated sialidosis patients was screened for mutations within the sialidase gene NEU1. Five novel mutations were identified. Four are missense and one is nonsense: c.674G>C (p.R225P), c.893C>T (p.A298V), c.3G>A (p.M1?), c.941C>G (p.R341G), and c.69G>A (p.W23X). We have used our findings and diagnostic tools to confirm the presence of a homozygous null allele in a neonate sibling. Recombinant adenoviruses expressing the mutant sialidase alleles in primary cell cultures were utilized to assess the impact of each mutation on enzyme activity and intracellular localization. None of the mutant alleles expressed significant enzymatic activity. The p.R341G mutation exerts its pathological effect by perturbing substrate binding, while the p.A298V and p.R225P mutations appear to impair the folding of the sialidase enzyme. Our findings point to mutation‐sensitive amino acids involved in catalytic function or structural stability and indicate the potential utility of these mutations for molecular diagnosis of this rare disease. Hum Mutat 23:32–39, 2004. © 2003 Wiley‐Liss, Inc.     

Mucolipidosis I — A sialidosis

Mucolipidosis I is characterized by Hurler-like features and skeletal dysplasia with a cherry-red macular spot and signs of neurodegeneration involving neuronal cells and myelin. Excessive amounts of sialic acid-containing compounds were found in cultured fibroblasts, leukocytes, and urine of a patient with a clinical phenotype of mucolipidosis I. In cultured fibroblasts, profoundly diminished activity of an α-N-acetylneuraminidase (sialidase) was found. Mucolipidosis I thus appears to be a distinct disorder of complex carbohydrate catabolism caused by the genetic deficiency of a neuraminidase.     

Evaluation of urinary cells in acid cholesteryl ester hydrolase deficiency

Deficiency in the lysosomal enzyme responsible for cholesteryl ester hydrolysis, acid cholesteryl ester hydrolase (E.C. 3.1.1.13), leads to two clinically recognized diseases: Wolman disease and cholesteryl ester storage including leukocytes, fibroblasts and liver. Analysis of urinary sediment from well characterized cases of Wolman disease and CESD also revealed the shedding of lipid enriched renal tubular cells. Morphologic, enzymic and lipid compositional studies of these cells indicate that the enzyme deficiency observed in fibroblasts and leukocytes from these individuals are reflected in these cells shed in the urine. These findings in renal tubular cells confirm and extend those made in other cell types. These studies indicate that analysis of urinary sediment in suspected cases of acid cholesteryl ester deficiency may provide a meaningful approach for monitoring therapeutic attempts involving enzyme infusion and gene therapy.     

Fatal infantile hypertrophic cardiomyopathy secondary to deficiency of heart specific phosphorylase b kinase

We describe here a male infant with a rare form of glycogenosis caused by deficiency of heart specific phosphorylase b kinase. The disease phenotype was characterized by severe glycogenosis restricted to the heart muscle with secondary rapidly progressive hypertrophic cardiomyopathy causing death at the age of 47 days.     

Infantile autism, fragile (X) (q27.3) and RFLP analysis in an extended Swedish family

In an extended family with eight individuals with infantile autism, in association with other developmental disorders and fragile (X) (q27.3), DNA techniques were used to investigate linkage between X chromosomal probes and the disorder. F9 was not informative and recombination was found between fragile X and DXS15, DXS51 and DXS52.     

Defective T-cell differentiation in acquired immune deficiency syndrome (AIDS)

A decline in T-cell lymphocyte number is the central characteristic of acquired immune deficiency syndrome (AIDS). The reason for the loss of these cells is not well understood. We investigated the hypothesis that defects in T-cell differentiation contributed to T-cell loss using anin vitro colony assay that measures T-cell precursor (CFU-T) frequency. The results indicate a substantial generalized decrease in CFU-T in people with AIDS (P<0.01), most of whom have Kaposi's sarcoma, and an occasionally severe decrease in CFU-T in people with ARC. Some of the cells from low colony formers suppressed colony formation by control cells. In addition, plasma from people with AIDS was less supportive of colony growth than control plasma. Decreased Ia expression on adherent mononuclear cells did not correlate with colony formation. A defect in T-cell repopulation can help explain the loss of T cells associated with AIDS.     

Identification of heterozygotes for glycogenosis 2 (Acid maltase deficiency)

In 21 obligate and 9 possible heterozygotes for acid maltase deficiency (AMD) (glycogenosis 2, Pompe's disease), different methods of identifying heterozygotes have been studied. Heterozygosity could not be demonstrated by physical examination, serum CPK assays, morphological examination of a muscle biopsy (including light-microscopy, histochemistry and electron-microscopy), or by ultrastructural examination of a skin biopsy. Heterozygotes could be identified to a large, but still limited extent, by measuring the acid α-glucosidase activity in urine, cultivated fibroblasts, leucocytes, or skeletal muscle. Heterozygotes for the generalized form of AMD could not be distinguished from those for the muscular form. The limitations of heterozygote identification by means of enzyme assays are discussed, and some practical aspects for genetic counselling are mentioned.     

Neuraminidase deficiency in the original patient with the Goldberg Syndrome

Homogenates of cultured skin fibroblasts from a non-ambulatory, 20-year-old male with cherry-red spots, corneal clouding, seizures, mental retardation, dysostosis multiplex, dwarfism, coarse facies and loss of vision, originally described by Goldberg et al. (1971), have diminished neuraminidase activity and an excess of neuraminic acid-rich compounds. Specifically, these cells have 2-17% normal neuraminidase when measured with 2-(3' methoxyphenyl)-N-acetyl-alpha-neuraminic acid, N-acetyl-neuramin-lactose and fetuin. Activities of 12 other lysosomal enzymes were either at or above the range of normal control fibroblasts. Total neuraminic acid concentration was 44.3 nmol/mg protein versus an average control value of 14.2. It is concluded that the Goldberg syndrome should be considered, along with mucolipidosis I and the cherry-red spot -- myoclonus syndrome, as resulting from a primary neuraminidase deficiency.     

Storage of alpha-1-antitrypsin in intrahepatic bile duct cells in alpha-1-antitrypsin deficiency (Pi Z phenotype)

Storage of alpha-1-antitrypsin (AAT) has been found in a small number of bile duct cells in liver tissue specimens from patients with Pi MZ, Pi SZ and Pi ZZ phenotypes. The storage appeared in the form of intracellular AAT immunoreactive inclusions. On EM investigation, AAT-like material was detected within cisternae of the RER and SER. Such AAT inclusions were found in proliferating bile ductules in conditions such as cirrhosis, focal nodular hyperplasia and extrahepatic obstruction. They were also observed in normal biliary structures at the level of the canals of Hering, bile ductules and interlobular ducts in 13 out of 47 cases. These findings are interpreted as indicating that the intrahepatic bile duct cells are a further source of AAT, and that in case of defective export of AAT from the cell, as is the case for the Z protein, the protein accumulates not only in hepatocytes but in biliary cells as well.     

Class II (DR) antigen expression on CD8+ lymphocyte subsets in acquired immune deficiency syndrome (AIDS)

In a selected group of human immunodeficiency virus (HIV)-infected patients we confirm the expansion of a CD8⁺ T-lymphocyte subset, i.e., the CD8⁺/Leu7⁺ cells, which account for 30% of the lymphocytes, compared to 3% in the control donors. In addition, a CD8⁺ T-lymphocyte subset that coexpresses class II (DR) antigens, i.e., CD8⁺/DR⁺ cells, is also increased from 1.5% in controls to 27% in the HIV-infected patients. Using three-color immunofluorescence and flow cytometry we can demonstrate that the CD8⁺/Leu7⁺ and the CD8⁺/class II⁺ cells are not distinct but overlapping subsets. In the HIV-infected patients 42% of the CD8⁺/Leu7⁺ cells were strongly positive for class II and these CD8⁺/Leu7⁺/class II⁺ cells accounted for 13% of all lymphocytes. These findings indicate that the expanded CD8⁺/Leu7⁺ cells are activated and hence might be actively involved in immune defense in acquired immune deficiency syndrome (AIDS).     

Biochemical genetics of the Lapland dog model of glycogen storage disease type II (acid α-glucosidase deficiency)

A recently described canine model (Lapland dog) of glycogen storage disease type II (GSD II, Pompe disease, acid α-glucosidase deficiency) was identified with several biochemical genetic methods. Complementation studies in which fibroblasts from a GSD II dog were fused with fibroblasts derived from control dogs and from human patients with different clinical forms of the disease did not lead to restoration of acid α-glucosidase activity in the heterokaryon cell populations. These results indicate that acid α-glucosidase deficiency is the primary defect in canine GSD II and that there is a close genetic parallelism with human GSD II. Immunotitration analysis of the residual acid α-glucosidase activity in the canine GSD II fibroblasts and liver demonstrated that this residual activity was not due to acid α-glucosidase enzyme, in which respect canine GSD II was similar to the infantile form of the human disease. Double immunodiffusion studies showed the presence of catalytically inactive acid α-glucosidase enzyme protein in canine GSD II. This is consistent with a structural gene mutation. It is concluded that canine GSD II in the Lapland dog is a homologous model of the infantile form of human GSD II, a conclusion in concordance with clinical and pathological studies.