bone marrow infiltration in langerhan’s cell histiocytosis - an unusual but important determinant for staging and treatment

background: langerhans' cell histiocytosis (lch) is a reactive proliferative disease of unknown pathogenesis characterized by proliferation of langerhans cells. involvement of bone marrow (bm), liver and lung are related to high risk factors and poor survival. the aim of this report is to highlight the clinical and haematological findings of 5 cases of lch with bm infiltration which may help to predict involvement of bm. case series: five cases of langerhan’s cell histiocytosis with bone marrow infiltration were retrieved from archives of department of hematology, pgimer and chandigarh for review and further analysis.male to female ratio was 3:2 with mean age of 9.4 months. two out of 5 patients had obvious skull swelling; however, radiography of the skull revealed lytic lesion of skull in 4 cases and 2 had skin rashes. hepatomegaly was present in 4 cases and 2 of whom also had lymphadenopathy and splenomegaly. all patients had anaemia at the time of presentation. bone marrow aspiration and trephine biopsy in all 5 cases revealed infiltration by large histiocytes with abundant cytoplasm and coffee bean shaped nucleus. nodules of these langerhans cells with admixture of eosinophils were seen on trephine biopsy. immunohistochemistry showed positivity for cd1a stain. conclusion: bm evaluation is important in lch patients to categorize disease which further determines the type of therapy to be given. clinical details may help to predict the bm involvement; however, demonstration of cd1a positive cells in marrow is most important tool to diagnose marrow infiltration by lch.