Simultaneous deficiency of sphingolipid activator proteins 1 and 2 is caused by a mutation in the initiation codon of their common gene. - Schnabel,D.; Schröder,M.; Fürst,W.; Klein,A.; Hurwitz,R.; Zenk,T.; Weber,J.; Harzer,K.; Paton,B.C.; Poulos,A.; Suzuki,K.; Sandhoff,K. (J Biol Chem, 1992)