Gm1-Gangliosidosis, Type Iii

A number sign (#) is used with this entry because type III GM1-gangliosidosis is caused by mutation in the gene encoding beta-galactosidase-1 (GLB1; 611458).

For a general discussion of classification and phenotypic heterogeneity of GM1-gangliosidosis, see type I (230500).

Description

GM1-gangliosidosis type III is an autosomal recessive lysosomal storage disorder characterized by neurodegeneration and mild skeletal changes. Age at onset ranges from 3 to 30 years. The disorder is less severe than GM1-gangliosidosis types I and II (230600). Type III shows extreme clinical variability, with some patients having only focal neurologic signs, such as dystonia, and others having more severe involvement with extrapyramidal signs and mental retardation. GLB1 enzymatic activity usually ranges from approximately 4 to 10% of control values (Suzuki et al., 2001).

Clinical Features

Wenger et al. (1974) described beta-galactosidase deficiency in young adults.

Loonen et al. (1974) reported a patient with type III GM1-gangliosidosis who had angiokeratoma beginning at age 8 years, cerebellar dysfunction and diminishing vision beginning at age 16, and myoclonic fits, intellectual deterioration and coarsening of the face beginning at age 22.

Suzuki et al. (1977) reported 2 Japanese sibs, aged 34 and 30 years, respectively, with the adult form of GM1-gangliosidosis. They had progressive pyramidal and extrapyramidal disease with generalized muscle atrophy without dysmorphism or macular cherry-red spots. Suzuki et al. (1978) found increased GM1 accumulation in cultured skin fibroblasts from these patients. However, the accumulation was less than that observed in patients with type I infantile disease, indicating a correlation of storage material with disease severity. By cell complementation studies, Suzuki et al. (1979) confirmed that the Japanese adults had a variant form of beta-galactosidase deficiency.

Stevenson et al. (1978) reported 3 patients from 2 families with type III GM1-gangliosidosis. All had onset by age 4 years, but showed survival into adulthood. One affected boy had early signs of stuttering, overactivity, mental retardation, spasticity, and ataxia. Radiographic examination at age 19 years showed scoliosis, irregularity of the vertebral plates, flattened vertebral bodies, and dysplastic femoral heads. Another child developed walking difficulties at age 3 and showed progressive deterioration with loss of speech and the development of choreic movements and progressive spasticity. The third patient began deteriorating at age 3 years. He never learned to speak clearly, developed abnormal hand movements, and showed mental retardation. He had generalized spasticity, athetoid movements, and rigidity. None of the patients had visceromegaly or macular red spots. Stevenson et al. (1978) stated that these patients had a more severe phenotype than usually seen in type III, but less severe than in types I and II.

Wenger et al. (1980) described a brother and sister, aged 19 and 25 years, respectively, with ataxia, mild intellectual deterioration, slurred speech, mild vertebral changes and little, if any, visceromegaly. A primary defect in beta-galactosidase was indicated by the half-normal values in many relatives, including both parents, and by the normal levels of sialidase. Complementation with infantile type I GM1-gangliosidosis did not occur, indicating that it was a variant form of that disorder. Chakraborty et al. (1994) provided follow-up of the family reported by Wenger et al. (1980). The 38-year-old sister and 32-year-old brother had normal childhood development but delayed or defective speech development. Neurologic workup of the sister at age 19 showed a defect in articulation and impairment of upper and lower limb coordination. At age 38, she showed a severe and progressive stutter, hyperactive deep tendon reflexes, especially in the legs, and pes cavus. Intelligence, cranial nerve function, and funduscopic examination were all normal. Bilateral total hip replacement had been required at the age of 33 years. The brother showed progressive dysarthria, moderate ataxia, and intention tremor, but cranial nerve funduscopic examinations were normal. Flattening of vertebral bodies, progressive kyphosis, and subluxation of the right hip were features. Both sides of the family originated from a small town in western Denmark.

Goldman et al. (1981) and Kobayashi and Suzuki (1981) reported a 27-year-old man with GM1-gangliosidosis who experienced a slowly progressive dystonia that began at about age 4 years. Dystonia primarily affected the face and limbs and eventually became incapacitating. Myoclonus, seizures, and macular cherry-red spots were never observed. Postmortem examination revealed intraneuronal storage, localized predominantly to the basal ganglia, in which neurons contained round, multilamellated inclusions. Other areas of the central nervous system appeared relatively unaffected, although small basilar dilatations were observed in scattered cortical pyramidal neurons and Purkinje cell dendrites showed focal swellings. Vacuolated cells of the reticuloendothelial system were observed, including Kupffer cells and histiocytes in the spleen, marrow, and intestinal tract. Biochemical analysis revealed a generalized beta-galactosidase deficiency with specific accumulation of GM1 ganglioside in the basal ganglia.

Uyama et al. (1992) described 3 Japanese brothers with type III GM1-gangliosidosis presenting as dystonia. The patients were examined at ages 28, 31, and 33 years. They had developed dysarthria with facial grimacing in early childhood. As adults, all had generalized dystonia that did not disappear when the patients were lying or sitting relaxed. Brain imaging showed bilaterally symmetric high density lesions only in the putamen.

Yoshida et al. (1992) reported 16 Japanese patients with adult GM1-gangliosidosis from 10 unrelated families. Age at onset ranged from 3 to 30 years. The main clinical manifestations were gait and speech disturbances caused by persistent muscle hypertonia. Dystonic posturing, facial grimacing, and parkinsonism were commonly seen. Dysmorphism, visceromegaly, and severe mental impairment were not observed.

Chakraborty et al. (1994) reported a 21-year-old patient with type III GM1-gangliosidosis who presented at age 3 years with speech difficulties that continued as a severe stutter. Neurologic examination demonstrated spastic quadriparesis, especially in the legs, with a scissoring gait. The patient had a history of urinary incontinence. Cranial nerve and funduscopic examinations, as well as intellect, were normal. Magnetic resonance imaging showed mild ventricular enlargement. The patient was also described as having short stature and scoliosis.

Biochemical Features

Early complementation studies on cells from patients with types I, II, and III GM1-gangliosidosis yielded conflicting results. Although mutant beta-galactosidase-1 in the different types is due to allelic mutations at the same locus, some studies showed complementation between the different types (see, e.g. Galjaard et al. (1975, 1975) and Koster et al., 1976; Reuser et al., 1979). However, in a detailed review, O'Brien and Norden (1977) discussed several possible explanations for the finding of complementation between different types of GM1-gangliosidosis, including alterations of tertiary structure and protein-protein interaction between different mutant monomers. O'Brien and Norden (1977) argued that the findings of complementation did not necessarily imply that the different types of GM1-gangliosidosis were nonallelic.

Taylor et al. (1980) reported biochemical studies of 2 of the patients reported by Stevenson et al. (1978). Beta-galactosidase differed in pH optima, heat denaturation, NaCl kinetics, and electrophoretic mobility from each other and from the normal. No complementation was found in cell fusion studies. The authors concluded that the 2 patients had different primary mutations at the beta-galactosidase locus that were likely structural in nature.

Mutoh et al. (1988) demonstrated altered properties of the mutant enzyme and altered apparent molecular weights of the enzyme isolated from the liver of a patient with the adult form of GM1-gangliosidosis. The findings suggested that some patients with the adult form have a structurally altered enzyme.

Hoogeveen et al. (1986) showed that the mutations in some cases of infantile and adult forms of GM1-gangliosidosis interfere with the phosphorylation of precursor beta-galactosidase. As a result, the precursor is secreted instead of being compartmentalized into the lysosomes and further processed.

Molecular Genetics

In the affected sibs reported by Wenger et al. (1980), Chakraborty et al. (1994) identified compound heterozygosity for 2 mutations in the GLB1 gene (611458.0013; 611458.0022).

In 6 Japanese patients with the adult/chronic form of GM1-gangliosidosis, Nishimoto et al. (1991) identified a mutation in the GLB1 gene (I51T; 611458.0004).

Yoshida et al. (1991, 1992) also found the I51T mutation in Japanese patients with adult GM1-gangliosidosis. All patients except 1 were homozygotes. One patient was a compound heterozygote with an R457Q mutation (611458.0008). Clinically, the compound heterozygous patient showed more severe neurologic manifestations and a more rapid clinical course than did the homozygotes. The I51T allele showed 5.28 to 7.28% residual enzyme activity, whereas the compound heterozygous patient had 4.24% residual activity. The mutations causing residual enzyme activity appeared to be related to severity of clinical manifestations, but other genetic or environmental factors likely also contributed to the phenotype since there was considerable variation in age of onset and clinical course among I51T homozygotes.