Sex liability to single structural defects.

Forty-two of 52 single, localized defects of morphogenesis showed a nonrandom predeliction to one sex. For some of these malformations, the sex liability may be explained on the basis of normal anatomic or hormonal differences between the sexes. For example, the male excess of "prune belly" or triad syndrome is considered due to the fact that most cases are secondary to obstruction in the penile urethra, and the male excess of pyloric stenosis is hypothesized as being secondary to the muscle hypertrophying effect of testosterone in the male neonate. The sex differences for most of the defects suggest that genes on the X and/or Y chromosome exert a role in morphogenesis that extends well beyond the development of sex-related structures.