Excessive production of 1-deoxysphingolipids is thought to underlie neurotoxicity in several conditions, including HSAN1, type 2 diabetes, macular telangiectasia type 2, and chemotherapy-induced peripheral neuropathy (4–6, 8, 9, 11, 12, 25). Here, SPTLC1 is linked to macular telangiectasia type 2.