Skin-limited Langerhans' cell histiocytosis in children.

Langerhans' cells are dendritic cells derived from precursors in the bone marrow. They constitute 2-4% of the resident epidermal cells and are found within the epidermis above the basal layer. They function as immunologic cells by recognizing antigens and presenting them to T cell lymphocytes. Langerhans' cell histiocytosis is a rare pathology characterized by an abnormal clonal proliferation of Langerhans' cells that infiltrates different organs of the human body. The proliferating Langerhans' cells appears to be primarily responsible for the clinical manifestations. The stimulus for their proliferation is unknown. Among different organs, cutaneous involvement is encountered in 40% of cases. The aim of this investigation is to review the clinicopathologic, immunologic and ultrastructural features of skin-confined Langerhans' cell histiocytosis in children through seven case series. Four boys and two girls with age range of 1 year to 8 years presented with scaling, crusted papules, nodules and papulonodular lesions (two cases each). The locations included the face (three cases), scalp, trunk and vulva (one case each). The histological features included histiocytic reaction (one case), granulomatous reactions (three cases) and both granulomatous and histiocytic reactions (two cases). The diagnosis was confirmed by histochemical (S-100 + CD1a +) and ultrastructural studies (Birbeck granules). Langerhans' cell histiocytosis is a rare disease with pleomorphic cutaneous clinical expressions. Three types of skin lesions usually occur: nodules (common), scaling, or crusted papules (next in frequency) and finally soft, yellow papular xanthomas (rare). Three types of histological pictures are seen: histiocytic, granulomatous (common) and xanthomatous (rare).