Aplasia cutis congenita and antithyroid drugs.

A congenital defect of the scalp is an uncommon entity occurring in one in 2000 deliveries. It may present certain diagnostic problems in the newborn infants. In this era of invasive intrapartum fetal monitoring, Obstetricians should be made aware of this entity as in its limited form aplasia cutis congenita (ACC) could easily be mistaken for damage inflicted by spiral electrodes. The late scarring observed occasionally after the application of Willet's forceps may also mimic this defect. The defect tends to be familial in majority of the cases. Relation of this scalp anomaly with in utero exposure to antithyroid drugs is still a matter of debate. We report a child with ACC whose mother was treated with neomercazole during pregnancy. As there was no history of similar defects in other siblings, a causal role for neomercazole is suspected.