Adult onset folliculocentric langerhans cell histiocytosis confined to the scalp.

Langerhans cell histiocytosis (LCH) is a pleomorphic disease entity characterized by local or disseminated atypical Langerhans cells found most commonly in bone, lungs, mucocutaneous structures, and endocrine organs. Cutaneous disease occurs in approximately one quarter of all cases. Cutaneous findings include soft-tissue swelling, eczematous changes, a seborrheic dermatitis-like appearance, and ulceration. We report a rare case of LCH confined to the scalp with folliculocentric infiltrates. This 32-year-old male patient presented with follicularly based erythema, scale, and pustules unresponsive to topicals and oral antibiotics. The patient's lesions mimicked lichen planopilaris and folliculitis decalvans during the disease process. On hematoxylin and eosin stain, scalp biopsy showed a perivascular interstitial patchy lichenoid mononuclear cell infiltrate that focally abutted follicular infundibula. Prominent mononuclear cells having reniform nuclei were present, and immunoperoxidase stains for CD1a confirmed Langerhans cell differentiation. Serological and imaging workup failed to display systemic involvement.