[Adult Sandhoff disease presented as a motor neuron disease phenotype with slow progression]

A 35-year old Japanese male with adult Sandhoff disease was described, who was presented as a motor neuron disease phenotype with slow progression. At the age of 15, he first noticed weakness in his thigh. At the age of 28, his upper and lower motor neuron disturbances were disclosed. He was diagnosed as atypical amyotrophic lateral sclerosis. At the age of 34, a slight sensory disturbance appeared in the lower extremities. When he was admitted to our hospital, he displayed marked atrophy and weakness in his quadriceps femoris muscles, but no signs of mental deterioration and cerebellar ataxia. Because of the atypical course of motor neuron disease, hexosaminidase activity in peripheral leukocytes was determined. The assay of total hexosaminidase, hexosaminidase A and hexosaminidase B activities demonstrated low levels of these activities (7-15% of controls), leading the diagnosis of Sandoff disease. He was a member of non-consanguineous family, and the abnormal patterns of hexasaminidase activities were different between his father and mother. These data appear to show that he is a compound heterozygote in the locus of the hexosaminidase B gene. This is the first Japanese case of adult Sanhoff disease presented as a motor neuron disease phenotype.