Occurrence of thanatophoric dysplasia type I (R248C) and hypochondroplasia(N540K) mutations in two patients with achondroplasia phenotype

We report two patients with clinical and radiological findings of achondrop lasia, who had the most common FGFR3 mutation occurring in thanatophoric dy splasia type I and hypochondroplasia, respectively. Thanatophoric dysplasia is usually a lethal condition, but the patient carrying this mutation is a live and presents a medical history similar to that of patients with achond roplasia. The events leading to such a discrepancy between genotype and phe notype are unclear. These rare cases may influence an appropriate medical a nd genetic counseling. (C) 2001 Wiley-Liss, Inc.