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APLASTIC AND HYPOPLASTIC ANEMIAS

APLASTIC AND HYPOPLASTIC ANEMIAS. What happens when the bone marrow shuts down?. 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.

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APLASTIC AND HYPOPLASTIC ANEMIAS

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  1. APLASTIC AND HYPOPLASTIC ANEMIAS What happens when the bone marrow shuts down?

  2. 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.

  3. HYPOCELLULAR BONE MARROW IN APLASTIC ANEMIA

  4. APLASTIC ANEMIA • Pathophysiology: • The primary defect is a reduction in or depletion of hematopoietic precursor stem cells with decreased production of all cell lines. This is what leads to the peripheral pancytopenia. • This may be due to quantitative or qualitative damage to the pluripotential stem cell. • In rare instances it is the result of abnormal hormonal stimulation of stem cell proliferation • or the result of a defective bone marrow microenvironment • or from cellular or humoral immunosuppression of hematopoiesis.

  5. Pathophysiology of aplastic anemia

  6. APLASTIC ANEMIA • Etiology • Acquired • Most cases of aplastic anemia are idiopathic and there is no history of exposure to substances known to be causative agents of the disease • Exposure to ionizing radiation – hematopoietic cells are especially susceptible to ionizing radiation. • Whole body radiation of 300-500 rads can completely wipe out the bone marrow. • With sublethal doses, the bone marrow eventually recovers. • Chemical agents – include chemical agents with a benzene ring, chemotherapeutic agents, and certain insecticides. • Idiosyncratic reactions to some commonly used drugs such as chloramphenicol or quinacrine.

  7. APLASTIC ANEMIA • Infections – viral and bacterial infections such as infectious mononucleosis, infectious hepatitis, cytomegalovirus infections, and miliary tuberculosis occasionally lead to aplastic anemia • Pregnancy (rare) • Paroxysmal nocturnal hemoglobinuria – this is a stem cell disease in which the membranes of RBCs, WBCs and platlets have an abnormality making them susceptible to complement mediated lysis. • Other diseases – preleukemia and carcinoma

  8. PNH

  9. APLASTIC ANEMIA • Congenital disorders • Fanconi’s anemia – the disorder usually becomes symptomatic ~ 5 years of age and is associated with progressive bone marrow hypoplasia. • Congenital defects such as skin hyperpigmentation and small stature are also seen in affected individuals. • Familial aplastic anemia – a subset of Fanconi’s anemia in which the congenital defects are absent. • Clinical manifestations • Fatigue • Heart palpitations • Pallor • Infections • Petechiae • Mucosal bleeding

  10. APLASTIC ANEMIA • Lab findings • Severe pancytopenia with relative lymphocytosis (lymphocytes live a long time) • Normochromic, normocytic RBCs (may be slightly macrocytic) • Mild to moderate anisocytosis and poikilocytosis • Decreased reticulocyte count • Hypocellular bone marrow with > 70% yellow marrow • Treatment – in untreated cases the prognosis is poor • Remove causative agent, if known • Multiple transfusions • Bone marrow transplant

  11. RELATED DISORDERS • Disorders in which there is peripheral pancytopenia, but the bone marrow is normocellular, hypercellular, or infiltrated with abnormal cellular elements • Myelopthesic anemia – replacement of bone marrow by fibrotic, granulomatous, or neoplastic cells

  12. RELATED DISORDERS • Myelodysplastic syndromes – are primary, neoplastic stem cell disorders that tend to terminate in acute leukemia. • The bone marrow is usually normocellular, or hypercellular with evidence of qualitative abnormalities in one or more cell lines resulting in ineffective erythropoiesis and/or granulopoiesis and/or megakaryopoiesis. • The peripheral smear shows dysplastic (abnormality in development) cells including nucleated RBCs, oval macrocytes, pseudo-Pelger-Huet PMNs (hyposegmented neutrophils) with hyperchromatin clumping, hypogranulated neutrophils, and giant bizarre platlets. • Hypersplenism – why can this lead to pancytopenia?

  13. PURE RED CELL APLASIA • Pure red cell aplasia is characterized by a selective decrease in erythroid precursor cells in the bone marrow. WBCs and platlets are unaffected. • Acquired • Transitory with viral or bacterial infections • Patients with hemolytic anemias may suddenly halt erythropoiesis • Patients with thymoma – T-cell mediated responses against bone marrow erythroblasts or erythropoietin are sometimes produced.

  14. PURE RED CELL APLASIA • Congenital • Diamond-Blackfan syndrome – occurs in young children and is progressive. It is probably due to an intrinsic or regulatory defect in the committed erythroid stem cell.

  15. OTHER HYPOPROLIFERATIVE ANEMIAS • Renal disease – due to decreased erythropoietin • Endocrine deficiencies – may lead to decreased erythropoietin production. • For example: hypothyroidism leads to decreased demand for oxygen from tissues; decreased androgens in males; decreased pituitary function

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