A neonatal pustule:Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare, clinically heterogeneous disease that most commonly occurs in pediatric populations. Congenital self-limited LCH is a benign variant of LCH. It most commonly presents as a diffuse eruption and reports of single lesion cases are infrequent in the literature. Even in the case of congenital self-limited LCH, there is potential for future multisystem relapse, making long-term follow-up important. We present a case of single lesion self-limited LCH in a full-term male infant with interesting morphology. Physical examination revealed a painless, 6 millimeter, well-demarcated, papule encircled by erythema with central hemorrhage. An infectious workup was negative and a punch biopsy was obtained, which showed a dermal infiltrate of histiocytes consistent with a diagnosis of LCH. The lesion healed without intervention within three weeks. Our case highlights the need for dermatologists to consider LCH in the differential diagnosis for lesions of varying morphology in children, as proper identification is necessary to monitor for multisystem recurrence.