CSTA and Hyperkeratosis: The acne susceptibility signal at 3q21.1 shares a common causal variant with skin eQTLs for CSTA with high probability (PPSE = 0.95, PPNSE = 0.98), with the acne risk allele lowering expression of CSTA. Homozygous loss-of-function of CSTA causes a peeling skin syndrome that results from extensive hyperkeratosis (OMIM:607936).