A high RBC count combined with a low mean volume generally is attributed to thalassemia minor, either a or β, or to polycythemia vera with iron deficiency. Among 330 patients with a mean corpuscular volume (MCV) less than 70 cuμ, 35 had increased RBC counts. Of these, 26 had thalassemia minor and four had polycythemia vera. Five had secondary polycythemia (four from hypoxia, one from hypernephroma) with incidental iron deficiency. In the four of these patients given iron, the RBC count remained above normal and the MCV rose to normal. The RBC size distribution curves reliably distinguished between thalassemia minor and polycythemia with iron deficiency.
(JAMA 238:2391-2392, 1977)
Bessman JD. Microcytic Polycythemia: Frequency of Nonthalassemic Causes. JAMA. 1977;238(22):2391–2392. doi:10.1001/jama.1977.03280230055022
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