Most common site of histiocytosis is
Ans. is 'a' i.e. bone Histiocytosis is a disorder of the mononuclear phagocytic system.Mononuclear phagocytic system consists of monoblasts, promonocytes, monocytes and tissue macrophages.Macrophages are transformed monocytes i.e. monocytes present in the tissues. Monocytes emigrate continuously from peripheral blood into the tissuesHistiocyteThe term histiocyte is synonymous with macrophage.In diseases of mononuclear phagocytic system the terms histiocyte and histiocytosis are used.Langerhans cellsLangerhans cell is macrophage and plays important role in immunity.It processes antigen and present it to T cells.Langerhans cells histiocytosis (LCH) is a clonal histiocytosis and the lesions are characterized by the presence of Langerhans cells, eosinophils and Lymphocytes in a variable number.The various features of Langerhans cells are:Presence of Birbeck granules (E/M - HX bodies)Presence of enzymes likea Naphthyl acetate esterasea Naphthyl butyrate esteraseAcid phosphataseMarkers likeS-100 positivityCD-I a positivityHCA-DR expressionEarlier the term histiocytosis X was used which includedLetterer-Siwe diseases (generalised disease)Hand schuller-christian diseaseEosinophilic granuloma (localised lesion)However, now the term Langerhans cell histiocytosis is preferred Langerhans cell histiocytosis includes 3 clinicopathologic entitiesAcute disseminated Langerhans cell histiocytosisMultifocal Langerhans cell histiocytosisUnifocal Langerhans cell histiocytosisAcute disseminated LCH (Letterer siewers disease)* This is the most severe form with systemic lesionsUsually affects children < 2 yearsSeborrheic type of skin rash is present over the front and back of the trunk and scalpHepatosplenomegaly is moderateLymphadenopathy is positivePulmonary lesions are not uncommonLytic lesions in bones are seenFever is of moderate degreeOtitis media andMastoiditis may be present Hematological findings of LCH CytopeniasAnemia, neutropenia and thrombocytopenia. These may occur in isolation or in combination.Cytopenias occur because hematopoietic cells in marrow get replaced by histiocytes.Bone marrowBone marrow shows infiltration by histiocytes which are large cells with abundant cytoplasm having a vesicular, oval or indented nucleus. These cells are loaded with cholesterol.E/M reveals Birbeck granulesS100, CD1a positiveMultifocal LCHMultiple lesions involving many systems.Prognosis is better than in the disseminated LCH.Usually affects children who presents with fever and skin eruptions on the scalp.Some of the patients demonstrate involvement of posterior pituitary stalk of hypothalamus resulting in diabetes insipidus.Some manifests proptosis of eye.There is evidence of osteolytic lesions in some of the bones like skull, orbit, jaw, femur, vertebrae and ribsHistomorphology of the lesion demonstrates histiocytes admixed with eosinophils.Unifocal LCHThis is characterized by a focal lesion amenable to treatment and carry a good prognosis.This focal disease affects the skeletal system.Commonly affected bones are calvaria, ribs and femur.The lesions may be asymptomatic or may cause pain, tenderness and pathological fractures.
Bone
Skin
Lung
Liver
Immunology and Rheumatology