What is the difference between megaloblastic anemia and macrocytic anemia

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Failures of cobalamin assays in pernicious anemia. N Engl J Med ; —6. Snow CF. Laboratory diagnosis of vitamin B12 and folate deficiency: a guide for the primary care physician. Arch Intern Med ; — Am J Hematol ; 89 —6. Green R, Dwyre DM. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology.

Anemia may occur from blood loss, decreased RBC production such as in iron deficiency, or increased RBC destruction such as in hemolysis. Management is aimed at improving Hb levels and treating the underlying conditions.

Anemia is a quantitative deficiency of Hb, the oxygen-carrying component of RBCs. Anemia is noted when Hb levels are approximately:. Anemia is most commonly classified into the subtype microcytic, normocytic, or macrocytic based on the size of the RBCs. These features are usually due to a decreased Hb content within the RBCs. Causes include:. Normocytic anemias have a normal MCV. Often, the reticulocyte count is used to help narrow the differential diagnosis. Causes of normocytic anemia include:.

Symptoms develop based on the rate and severity of Hb decrease from baseline. Anemia is also often asymptomatic and found on laboratory studies only. The diagnostic process typically starts by assessing the CBC, MCV, and reticulocyte count, which are best evaluated simultaneously to start narrowing the differential diagnosis. Peripheral blood smear of a patient with megaloblastic anemia: The red arrow points to a hypersegmented neutrophil. Left: schistocytes closed arrowheads Right: spherocytes open arrowhead and schistocytes open arrows.

If lifestyle factors are thought to be contributing to the anemia, education can be provided regarding:. Hemolytic anemias are result of the destruction or premature clearance of RBCs. Specifically, they can be due to either damage caused by a narrowed vascular lumen intravascular hemolysis or increased splenic clearance extravascular hemolysis.

Splenic clearance can result from intrinsic abnormalities of the RBCs e. None of the trademark holders are endorsed by nor affiliated with Lecturio. Lecturio Medical complements your studies with evidence-based learning strategies, video lectures, quiz questions, and more — all combined in one easy-to-use resource.

By continuing use of our service you agree upon our Data Privacy Statement. Your path to achieve medical excellence. Study for medical school and boards with Lecturio. Create your free account. Continue Learning. The Lecturio Medical Concept Library. Anemia: Overview. Last update:. May 11, am. Table of Contents.

Share this concept:. Share on facebook. Share on twitter. These enlarged, immature red blood cells called megaloblasts arise due to defective DNA production. Factors that cause disruption in DNA production in red blood cells also affect other types of cells such as the white blood cells in the bone marrow.

So, viewed through a microscope, both red and white cells in megaloblastic anemia appear abnormal. One of thecommon macrocytic anemia causes is medication, especially those that interfere with folate metabolism and absorption. These include methotrexate, a drug used to treat cancer and rheumatoid arthritis, anticonvulsants, anti-cancer drugs, HIV medications, antidiabetic drugs metformin and antimicrobials. Vitamin B12 deficiency takes years to develop because of the large stores of the substance in the liver.

Causes may include autoimmune Addisonian pernicious anemia, complication of surgery such as ileocolic resection or gastrectomy, HIV infection, bacterial overgrowth, parasitic infestation, dietary deficiency, and pernicious anemia which is a condition common in the elderly.

Folate deficiency may be due to dietary deficits, malabsorption, hemolysis, leukemia, some skin diseases, pregnancy, increased urinary excretion of folate related to acute hepatitis, heart failure, and dialysis. Drugs causing folate deficiency include anticonvulsants, alcohol, methotrexate, trimethoprim and sulfasalazine. Causes of non-megaloblastic macrocytic anemia are not related to defective DNA synthesis.

Non-megaloblastic macrocytic anemia is less common and is characterized by the absence of megaloblasts, and instead, the presence of mature but large red blood cells. This type of red blood cells is normally seen in newborns only.

Causes include:. Treatments depend on the macrocytic anemia causes and type of anemia involved. Proper evaluation and diagnosis are necessary and this may be done with the aid of a test called peripheral blood smear. A blood smear is examined under the microscope to see the size, shape and number of the red blood cells.

Megaloblastic macrocytic anemia is characterized by the presence of Howell-Jolly bodies that appear assmall specks inside the red blood cells. These indicate that these are immature red blood cells that have been released from the bone marrow into the blood stream to compensate for anemia.