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A 3-year-old boy presented with history of fever, failure to thrive, weight loss and bone pains since one month. Physical examination reveal pallor and hepatosplenomegaly. His CT scan revealed “multiple focal lytic lesions in spine”. Complete blood counts was as follows: Hb: 7.6 g/dL, Hct: 24.6 %, MCV: 69.6 fL, MCH: 21.4 pg, WBC: 10.7 X 10E9/L, ANC: 7.2 X 10E9/L and Plt: 400 X 10E9/L. Peripheral blood smear revealed hypochromic microcytic red blood cells, white blood cells and platelets were normal, while bone marrow aspirate was cellular with trilineage hematopoiesis and bone trephine biopsy showed areas of distorted architecture with increase in background fibrosis and histiocytes (panel A), expressing S-100 (panel B), CD1a (panel C) and CD68 (panel D) immuno-histochemical stains. In view of clinical details and bone marrow findings, overall findings were suggestive of Langerhans cell histiocytosis (LCH).
Langerhans cell histiocytosis (LCH) is a rare histiocytic disorder most commonly characterized by single or multiple osteolytic bone lesions demonstrating histiocytes along with macrophages, lymphocytes and eosinophils infiltrating nearly every organ. LCH is derived from myeloid progenitor cells from the bone marrow. Langerhans cell histiocytes’ identity must be confirmed either by positive immunohistochemical staining for CD1a and CD207 or by the identification of Birbeck granules by electron microscopy.