Differences between etiologies of anemia resulting from impaired RBC production

on 4.3.09 with 0 comments

  • Stem cell failure

    • Aplastic anemia

      • Pancytopenia with marked bone marrow hypoplasia; splenomegaly and reticulocytosis is characteristically absent (because problems are in the bone marrow)

      • Patients are at risk for bacterial infections (due to neutropenia), bleeding (from thrombopenia), and acute leukemia (this is a stem cell thing)

      • Causes

        • Most are idiopathic (65%)

        • Most of the cases of known etiology follow exposure to myelotoxic drugs

        • Other known causes are insecticides, whole body irradiation, and infections like HIV, CMV, EBV, VZV, parvovirus B19, and viral hepatitis

      • If they are known, w/d of causative agents may be curative; marrow transplantation has been effective in younger patients, whereas older adults may benefit from immunosuppression

      • Proposed mechanisms

        • Immunologically-mediated suppression of marrow stem cells via the secretion of inhibitory cytokines like IFN- and TNF- by activated T cells (T cell response thought to be due to antigenic alteration of stem cells after exposure to environmental insult)

        • Intrinsic abnormality of stem cells from genetic damage (supported by occasional transformation to acute leukemia)

        • The environmental kind is more responsive to steroids

      • Hereditary bone marrow aplasia (Faconi’s anemia)

        • Rare, AR syndrome characterized by defects in DNA repair

        • May also see hypoplasia of the spleen, kidneys, and bones (especially of the thumbs and radii)

        • Kids with this are at high risk of developing leukemia and carcinomas

        • Bone marrow transplant will cure anemia, but won’t decrease the risk for CA

    • Pure red cell aplasia

      • Acute forms may be seen with chronic pre-existing hemolytic anemia (infection shuts down the overworked marrow) or as a drug or infection-related d/o (these 2 affect previously normal marrow); these are usually self-limited and referred to as transient erythroblastopenia of childhood

      • Chronic forms

        • Diamond-Blackfan syndrome: idiopathic and hereditary; marrow transplant is the only treatment

        • Associated with neoplasms like leukemia of large granular lymphocytes and thymoma (resection of thymoma may be curative in up to ½ of patients; in the others do plasmapheresis or immunosuppressive therapy)

    • Anemia of renal failure

      • Comes from decreased EPO production or from uremia and platelet dysfunction (latter may lead to bleeding and Fe deficiency)

      • Recombinant EPO is helpful

    • Anemia of endocrine d/o

      • Usually mild and asymptomatic

      • Seen with d/o of the thyroid, adrenal, nads, and pituitary

  • D/o of erythroblast proliferation and maturation

    • Megaloblastic anemias

    • Myelodysplastic syndromes

    • Fe deficiency

    • Sideroblastic anemias

      • Come from an Fe utilization defect with abnormal accumulation of hemosiderin in “ring sideroblasts” (Fe accumulates in the mitochondria around the nucleus)

      • May be idiopathic, hereditary, or drug-induced

    • Anemias of chronic disease

    • Myelophthisic anemia

Category: Medical Subject Notes , Pathology Notes



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