In humans, missense mutations in the conserved residues of the permease transporter GxxxD/E motif have also been detected in Gorlin's syndrome, a hereditary condition caused by familial mutations in PTCH (Chidambaram et al., 1996; Wicking et al., 1997; Aszterbaum et al., 1998). The gene discussed is PTCH1; the disease is nevoid basal cell carcinoma syndrome.