While covering for a colleague away on holidays, you receive the following laboratory results for...

These results show a significant anemia (Hb 80 g/L) with microcytosis (MCV 76 fL) and otherwise preserved cell lines (WBC at the upper end of normal; platelets normal). MCCQE objectives emphasize using CBC patterns to classify anemia and prioritize common causes. In a young woman, the most likely cause of microcytic anemia is iron deficiency , most often due to menstrual blood loss and/or inadequate iron intake, and it can be severe.

Leukemia and myelodysplasia typically present with abnormalities in multiple cell lines (e.g., leukocytosis with blasts or cytopenias) and are less consistent with an isolated microcytic anemia and normal platelets. Anemia of chronic disease is usually normocytic or mildly microcytic and is less likely to produce such a low hemoglobin without an obvious chronic inflammatory condition. Thalassemia trait classically has marked microcytosis with relatively preserved hemoglobin (often only mild anemia) and is suggested by a lifelong history and family/ethnic background. The next clinical step (at follow-up) would be iron studies (ferritin first) and assessment for bleeding sources.