normocytic
Summary
Normocytic refers to red blood cells (RBCs) of normal size, typically defined by a mean corpuscular volume (MCV) of 80–100 fL. Normocytic anemia is caused by conditions involving either decreased RBC production or increased RBC destruction/loss without affecting cell size.
Detail
Normocytic anemia is classified based on reticulocyte count and underlying mechanism. Causes include: (1) Acute blood loss (hemorrhage), (2) Hemolytic anemias (e.g., sickle cell disease, G6PD deficiency, hereditary spherocytosis, autoimmune hemolytic anemia) which typically show elevated reticulocyte count as bone marrow compensates, and (3) Anemia of chronic disease/inflammation, aplastic anemia, chronic kidney disease (decreased erythropoietin), and early iron deficiency or mixed nutritional deficiencies, which typically show low/normal reticulocyte count reflecting inadequate marrow response. Workup involves reticulocyte index, peripheral smear, haptoglobin, LDH, bilirubin, and Coombs test to distinguish hemolytic from hypoproliferative causes. Clinically, normocytic anemia is an important category to recognize because it narrows the differential and guides further testing (e.g., checking creatinine for CKD, inflammatory markers for anemia of chronic disease, or hemolysis workup panel). It's calculated via the Wintrobe indices from a CBC: MCV = (Hct/RBC count) × 10.
Sources
- First Aid for the USMLE Step 1
- Robbins and Cotran Pathologic Basis of Disease
- Harrison's Principles of Internal Medicine
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