It was first characterized by identification of a germ line mutation in the patched homolog 1 (PTCH1) gene in basal cell nevus syndrome, which was then reinforced by the discovery of mutations of PTCH1, smoothened homolog (SMO), and other genes related to the HH signaling pathway in sporadic BCC (20, 21). The gene discussed is PTCH1; the disease is nevoid basal cell carcinoma syndrome.