HEXA and GM1 gangliosidosis: Therefore, in cases in which the abnormal accumulation of each ganglioside is found in swollen neurons, a definitive diagnosis should ultimately be made using DNA extracted from the same paraffin-embedded specimen via the identification of pathogenic mutation(s) in the responsible genes: the GLB1 gene for GM1 gangliosidosis and the HEXA, HEXB, and GM2A genes for GM2 gangliosidosis.