Ans. is 'c' i.e., Langerhan's cell histiocytosis o Langherhans cells histiocytosis is a histocvtic. disorder most commonly characterized bv a single or multiple osteolytic bone lesions demonstrating infiltration with histiocytes.o Histiocytic disorders are derived from mononuclear phagocytic cells (macrophages) and dendritic cells which have several different originl and locations.o The generic term histiocyte refers to several types of cells including langherhan cells, monocytes/macrophages and dermal/interstitial dendritic cells.o Langherhans cells histiocytosis is so named because the morphology and the immunophenotype of the abnormal cells is similar to that of langherhans cells which are specialized dendritic cells found in skin and mucosa.o Gene expression array data have shown that skin langherhan cells is not the cell of origin for LCH rather it is a myeloid dendritic cell that express the same antigen (CDla, CD207) as the skin langherhans cells.o For now 'langherhan cell histiocytosis remains the preferred nomenclature, although new termanology may evolve when the precise origin of CD 207 cells in LCH is fully understood.o The historical terms histiocytosis X, letterer siwe disease, hand schuller Christian disease and diffuse reticuloendotheliosis should be abandoned.o The term eosinophilic granuloma can sometimes be used to describe pathology of langherhan s cells histiocytosis.Diagnosis of LCHo LCH is diagnosed upon biopsyo A biopsy of an osteolytic bone lesion or skin lesion is generally preferred.# Langherhan cells are recognized on the basis of morphological criteria# The identity must then be confirmed by either positive immunohistochemical staining for CD1a and CD207 by the identification of Birbeck granules.o Biopsy of involved tissue usually demonstrates heterogenous collection of langherhan cells with eosinophils, neutrophils, small lymphocytes and histiocytes.Morphology of the langherhan cells# Langherhan cells are large oval mononuclear cells with few cytoplasmic vacuoles, little or no phagocytic material and slightly eosinophilic cytoplasm.# Nucleus is prominent with fine chromatin and thin nuclear membranes with grooved folded or indented nuclear contours imparting twisted towel.# Unlike dermal langherhan cells these cells do not have dendritic cell processes.# Similar to dermal langherhan cells, those in LCH express the histiocyte marker CDla. S100 and CD207 and contain Birbeck granules.Birbeck granules# Intracytoplasmic rod shaped organelles with central striations that can be demonstrated on electron microscopy.# Occasionally there is terminal vesicular dilatation giving the Birbeck granules the appearance of "tennis racket". | ||||||||Bone (77%)Skin (39%)LyphnodesLiverSpleenOral mucosaLung (10%)CNS (16%)o Occurs in majority of patientso Usually asymptomatico Lytic 'punched' out lesiono Usually present as eczematous rasho Ulcerative lesions in axilla inguinal folds genitalia or perianal regiono Seborrhic dermatitiso Lymphadenopathyo Enlarged thymus or mediastinal nodeso Hepatic dysfunctiono Hepatomao Sclerosing cholangitiso Massive Splenomegalyo Cytopeniaso Intra oral masso Gingivitiso Mucosal ulcerso Loose teetho Non productive cough dyspnoea chest pain or constitutional symptomso Risk of CNS invol- ment varies with bone involvemento CNS inolve- ment occurs more with involvement of facial and anterior middle cranial fossao Diabetes insipidus and symptoms of neuro- degeneration