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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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