Mutations in the ANOS1 (KAL1) (MIM 300836), FGFR1 (KAL2) (MIM 136350) and GNRHR (MIM 138850) genes have been the most frequently reported, but there are now over 30 genes that have been associated with CHH. The gene discussed is FGFR1; the disease is cartilage-hair hypoplasia.