Hypertrophic pyloric stenosis in twins: same genes or same environments?

The aetiology of infantile hypertrophic pyloric stenosis (IHPS) remains obscure. Cases in twins, usually monozygotic, have been sporadically reported as evidence for the genetic origin of the disease. We present a case of IHPS in a pair of dizygotic male twins together with a review of the literature, focusing on the question of whether the twin cases actually support a genetic or an acquired nature of IHPS.