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Clinical findings were compared with the results of molecular analysis in 16 Japanese patients from 10 unrelated families with the adult/chronic form of GM1 gangliosidosis.Age of onset ranged from 3 to 30 years.Major clinical manifestations were gait and speech disturbances caused by persistent muscle hypertonia.Dystonic postures and movements,facial grimacing,and parkinsonian manifestations were commonly seen.Cerebellar signs,myoclonus,severe intellectual impairment,dysmorphism,or visceromegaly were observed.A common single-base substitution,51Ile(ATC)- Thr(ACC),reported in a previous study of ours,was confirmed in 14 patients by the Bsu36I restriction site analysis;one was a compound heterozygote with another mutation(457Arg[CGA]-Gln[CAA])and the others were homozygoes of this mutation.Clinically,the compound-heterozgous patient showed more severe neurological manifestations and a more rapid clinical course than those of homozygotes.The homozygoes showed considerable variations in the age of onset and subsequent clinical course.The 51Ilr-Thr mutant allele expressed a significant amount of B-galactosidase activity,whereas the 457Arg-Gln mutant allele expressed extremely low activity in human BM1 gangliosidosis fibroblasts.We conclude that these gene mutations causing different residual enzyme activities are related to the severity of clinical manifestations,but some other genetic or environmental factors contribute to clinical heterogeneity.The Bsu36I restriction site analysis was performed in 7 families and provided clear results for the diagnosis of heterozygotes as well as homozygotes of this specific clinical form of GM1 gangliosidosis.The technique is applicable to prenatal diagnosis and genetic counseling. |
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