Before revision: In addition to its classic infantile form, Tay Sachs disease may present in juvenile or adult onset forms, often as the result of compound heterozygosity between two alleles, one which would cause the classic infantile disease in homozygotes and another that allows some residual HEXA enzyme activity.
After revision: In addition to its classic infantile form, Tay Sachs disease may present in juvenile or adult onset forms, often as the result of compound heterozygosity between two alleles, one that causes the classic infantile disease in homozygotes and another that allows some residual HEXA enzyme activity.