Thanatophoric dysplasia (TD), a severe skeletal dysplasia, is virtually always lethal neonatally, although a few previous reports have documented survival up to 4.75 years. We present a patient with survival beyond age 9 years and summarize his growth, development and medical history. The common Arg248Cys mutation in the extracellular region of fibroblast growth factor receptor 3 (FGFR3) was identified, eliminating the possibility that his long‐term survival is attributable to an atypical mutation. This patient (and at least one other TD long‐term survivor) have a rare skin disorder, acanthosis nigricans, which also occurs in Crouzon syndrome when caused by a FGFR3 mutation. Therefore, any molecular model of the origin of acanthosis nigricans secondary to FGFR3 mutations must account for the association of diverse mutations and these cutaneous effects. Am. J. Med. Genet. 70:427–436, 1997. © 1997 Wiley‐Liss, Inc.