To date, over 322 mutations in the ARSA gene have been reported to cause metachromatic leukodystrophy, including 237 missense, 18 splicing, 31 small deletions, 20 small insertions, 6 small insertions/deletions, 6 gross deletions, 1 gross insertion, and 2 complex rearrangements, mostly affecting the C (alpha)-formylglycine. This evidence concerns the gene ARSA and metachromatic leukodystrophy.