Two independent PCR assays found a C-to-T mutation at coding nucleotide 206 resulting in a serine to leucine alteration in codon 69 (p.S69L). A second nucleotide C-to-T change results in a silent mutation at position 166. The result is a receptor that is overactive, though responsive to hormone regulation, and produces a greater activation of the MC1R effector, G protein-coupled adenylyl cyclase, than does the wild-type allele. (J:4636)