HEXA and Tay-Sachs disease: Tay Sachs disease (TSD) (MIM# 272800) is an autosomal recessive neurodegenerative disorder due to β-hexosaminidase A deficiency caused by mutation in the HEXA gene (MIM* 606869) encoding the α subunit of hexosaminidase A, a lysosomal enzyme composed of α and β polypeptides [1].