APLASTIC AND HYPOPLASTIC ANEMIAS Waggas Elaas

APLASTIC ANEMIA Aplastic anemia is a severe, life

threatening syndrome in which production of erythrocytes, WBCs, and platlets has failed.

Aplastic anemia may occur in all age groups and both genders.

The disease is characterized by peripheral pancytopenia and accompanied by a hypocellular bone marrow.

Pancytopenia : a reduction in blood count of all cell lines, WBCs, RBCs, platelets.

PATHOPHYSIOLOGY The underlying defect in all cases appears to be a

reduction in the number of haemopoieticpluripotential stem cells, and a fault in theremaining stem cells or an immune reaction

against them, which makes them unable to divide and differentiate sufficiently to populate the bone marrow

CAUSES OF APLASTIC ANAEMIA.Secondary PrimaryIonizing radiation:accidental exposure (radiotherapy, radioactive isotopes, nuclear power stations)

Congenital (Fanconi,s & Non Fanconi,s

Chemicals :benzene, organophosphates and other organic solvents, DDT and other pesticides, organochlorines, recreational drugs

Idiopathic acquired

Drugs: busulfan, chloramphenicol,Viruses: viral hepatitis (non-A, non-B, non-C, non-G in most cases), EBV

OTHER CAUSES OF PANCYTOPENIA Acute leukaemia Megaloblastic anaemia Paroxysmal nocturnal haemoglobinuria (PNH) Myelofibrosis Splenomegaly Myeloma or lymphoma

CLINICAL FEATURES At any age with a peak incidence around 30 years. A slight male predominance. symptoms and signs resulting from anaemia,

neutropenia or thrombocytopenia. Infections, particularly of the mouth and throat, are

common and generalized infections are life-threatening.

Bruising, bleeding gums, epistaxes and menorrhagia are frequent, and the usual presenting features, often with symptoms of anaemia.

The lymph nodes, liver and spleen are not enlarged.

LABORATORY FINDINGS Anaemia is normochromic, normocytic or

macrocytic The reticulocyte count is usually extremely low Leucopenia. There is a selective fall in

granulocytes,usually but not always to below 1.5 x 109/L.In severe cases, the lymphocyte count is also low.The neutrophils appear normal. Thrombocytopenia is always present and, insevere cases, is less than 20 x 109/L. There are no abnormal cells in the peripheral blood.

The bone marrow is hypocellular, with loss ofhaemopoietic tissue and replacement by fat whichcomprises over 75% of the marrow.The main cells present are lymphocytes and plasma

cells.Megakaryocytes in particular are severely reduced

or absent.

The disease must be distinguished from other causes of pancytopenia.

This is done by examination of the bone marrow samples for Cytogenetic analysis, flow-cytometry, and for morphology of cells and the marrow microenviromnent.

HYPOCELLULAR BONE MARROW IN APLASTIC ANEMIA

HYPOCELLULAR NORMOCELLULAR

RELATED DISORDERS1. Pure red cell aplasia Characterized by a selective decrease in erythroid precursor

cells in the bone marrow. WBCs and platlets are unaffected.2. Congenital dyserythropoietic anaemia. Hereditary refractory anaemias characterized by ineffective

erythropoiesis and erythroblast multinuclearity.3. Myelodysplastic syndromesprimary, neoplastic stem cell disorders that tend to terminate in

acute leukemia