Megaloblastic anemia

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Summary of Megaloblastic anemia

Megaloblastic anemia results from inhibition of DNA synthesis during red blood cell production. When DNA synthesis is impaired, the cell cycle cannot progress through the cell cycle properly, leading to cell growth without division, which presents as macrocytosis. Megaloblastic anemia has a rather slow onset, especially when compared to that of other anemias. The defect in red blood cell DNA synthesis is most often due to a deficiency of vitamin B12 and/or folic acid.

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Megaloblastic anemia

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NOTES NOTES MACROCYTIC ANEMIA GENERALLY, WHAT IS IT? PATHOLOGY & CAUSES ▪ Bone marrow produces larger than normal erythrocytes AKA red blood cells (RBCs) CAUSES ▪ Multifactorial: nutritional deﬁcits, genetics, substance exposure (e.g. certain drugs, alcohol) SIGNS & SYMPTOMS ▪ Fatigue, dyspnea, weight loss, pallor, impaired concentration/memory, diarrhea, onychoschizia (brittle nails) DIAGNOSIS LAB RESULTS ▪ ▪ ▪ ▪ ▪ Complete blood count Peripheral blood smear analysis Blood chemistry Iron studies Genetic testing TREATMENT ▪ Address underlying causes MEGALOBLASTIC ANEMIA osms.it/megaloblastic-anemia PATHOLOGY & CAUSES ▪ Macrocytic, normochromic anemia characterized by formation of large RBCs CAUSES Cobalamin and/or folate deﬁciency ▪ Impaired DNA synthesis during erythropoiesis → uncoordinated maturation of cytoplasm and nuclei in erythroblasts (nuclear-cytoplasmic asynchrony) → abnormally large RBCs (macrocytosis) + defective cells with fragile membranes → RBCs die prematurely → anemia B12 deﬁciency ▪ Insufﬁcient diet (e.g. vegan diet without B12 supplements, alcoholism, systemic/mental illness, food insecurity) ▪ Malabsorption ▫ Lack of intrinsic factor → pernicious anemia ▫ Surgical: gastrectomy, bariatric surgery → lack of absorptive surface → pernicious anemia ▫ Pancreatic insufﬁciency → impaired binding of B12 to intrinsic factor → pernicious anemia ▫ Medications that interfere with absorption: e.g. biguanides, H2 receptor blockers, proton-pump inhibitors, neomycin OSMOSIS.ORG 409

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Megaloblastic anemia

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are the two most common causes of megaloblastic anemia.

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A 25-year-old man comes to his primary care physician's office because of weakness and fatigue for the past 2 months. The patient also reports recent sensations of pins and needles in his lower extremities. Physical examination shows conjunctival pallor and atrophic glossitis. Laboratory results show a hemoglobin level of 9.0 g/dl and a mean corpuscular volume of 110 fl/red cell. Which of the following vitamin deficiencies may lead to megaloblastic anemia?

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