Aplasia Cutis Congenita

A 4-year-old girl presented with this scalp lesion, which had been present since birth. She received a diagnosis of aplasia cutis congenita.

Aplasia cutis congenita most commonly (70% of cases) manifests as a solitary defect on the scalp. The lesions are noninflammatory and well demarcated, and they range in size from 1 to 2 cm. 

Aplasia cutis congenita lesions may be circular or oval. The appearance of lesions varies depending on when they occur during gestation. Older ones appear as atrophic fibrotic scars with associated alopecia, as in our case, while more recent lesions appear ulcerated.

Most lesions occur close to the vertex and lateral to the midline, but similar defects can occur on the face, trunk, and limbs, where they often are symmetric. The depth of the lesions varies, with most involving the epidermis and upper dermis; however, aplasia cutis congenita lesions may extend deeper up to the dura.

Most patients appear to have no other abnormalities; however, aplasia cutis congenita can be found in association with other defects and various syndromes. Major complications are bleeding, local infection, and meningitis.

Aplasia cutis congenita can be differentiated from focal dermal hypoplasia, which is more common in girls, usually is linear in distribution, and often is associated with other abnormalities. Maternal ingestion of the teratogen methimazole, intrauterine herpes virus, and intrauterine varicella zoster virus have been associated with this condition.