Objective: To explore the clinical features and molecular mutation of HEXB gene in a case with juvenile Sandhoff disease.
Method: We retrospectively reviewed the clinical, neuroimaging and biochemical findings in this Chinese child with juvenile Sandhoff disease. Hexosaminidase A and hexosaminidase A & B activities were measured in blood leukocytes by fluorometric assay. HEXB gene molecular analysis was performed by PCR and direct sequencing.
Result: The 9-year-old boy was admitted for psychomotor regression. He presented slowly progressive gait disorder and dysarthria during the last three years. Cranial MRI revealed a marked cerebellar atrophy with normal intensity in the thalamus and basal ganglia. Brain MRS showed normal in the thalamus and basal ganglia. Hexosaminidase A was 69.5 (mg·h) [normal controls 150-360 nmol/(mg·h)], hexosaminidase A & B activity was 119 nmol/(mg·h)[normal controls 600-3 500 nmol/(mg·h)], confirming the diagnosis of Sandhoff disease. The patient was a compound heterozygote for a novel deletion mutation c.1404delT (p. P468P fsX62) and a reported mutation c.1509-26G>A.
Conclusion: The clinical features of juvenile Sandhoff disease include ataxia, dysarthria and cerebellar atrophy. The enzyme assay and molecular analysis of HEXB gene can confirm the diagnosis of Sandhoff disease. The novel mutation c.1404delT(p. P468P fsX62) is a disease-related mutation.