MFAP4 was first associated with Smith-Magenis syndrome (SMS, OMIM #182290), a rare sporadic disorder characterized by skeletal anomalies and intellectual deficit, which is predominantly caused by a 3.7 megabase (Mb) interstitial 17p11.2 deletion encompassing the MFAP4 locus1. The gene discussed is MFAP4; the disease is Smith-Magenis syndrome.