FGFR3 mutations cause wide spectrum of disorders ranging from skeletal dysplasias (hypochondroplasia, achondroplasia, and thanatophoric dysplasia), benign skin tumors (epidermal nevi, seborrhaeic keratosis, and acanthosis nigricans), and epithelial malignancies (multiple myeloma and prostate and bladder carcinoma). The gene discussed is FGFR3; the disease is skeletal dysplasia.