Focal facial dermal dysplasia or aplasia cutis congenita: a case with a hair collar.

Aplasia cutis congenita describes localized defects of skin that may have many causes. A 6-month-old male presented with bilateral atrophic patches on his cheeks distributed along a line from the preauricular area to the angle of the mouth. They had been present since birth. He had no other abnormalities detectable on examination and no family history of similar lesions. A distinct collar of long pale hairs surrounded the lesions, especially the largest one. Histology showed changes consistent with aplasia cutis congenita or focal facial dermal dysplasia. We propose our patient's lesions may be the result of failure of ectodermal fusion over embryological closure lines. This may be a distinct subgroup of atrophic facial lesions.