Gangliosidosis (GM2 Type I) – Japanese Chin

Gangliosidosis (GM2, B variant, type 1) is a fatal, progressive neurodegenerative lysosomal storage disease caused by a deficiency of β-hexosaminidase. The enzyme is composed of a dimer of two subunits α and β encoded by genes HEXA and HEXB. GM2 gangliosidosis can be caused by defects in the genes HEXA (Tays–Sachs disease, B-variant; where only the isoform A is deficient), HEXB (Sandhoff disease, O-variant; where both isoforms are involved). Mutations within the variants of β-hexosaminidase allow a build-up of toxic substances in the nerve cells (mainly neurons). An autosomal recessive mutation in HEXA is observed in the Japanese Chin dog (also known as Japanese Spaniël).