The proband we studied carried heterozygous missense mutations in two different genes important for hypothalamic/pituitary function, PROKR2 and WDR11. This finding implicates a putative digenic basis for PSIS in this child and also suggests that this unusual genetic mechanism may explain other cases of PSIS that lack conventional autosomal-recessive inheritance. This evidence concerns the gene WDR11 and pituitary stalk interruption syndrome.