Microcytosis associated with sickle cell anemia.

Sickle cell (Hb SS) anemia is considered a normochromic-normocytic hemolytic disorder. In 53 patients with Hb SS (mean reticulocyte values 16.8%), the authors observed that mean corpuscular hemoglobin (MCH) was 29.8 +/- 2.4 mu microgram and mean corpuscular hemoglobin (MCV) was 88.1 +/- 6.8 cu micrometers. In contrast, patients in a comparable hemolytic-disease group unrelated to hemoglobinopathies (mean reticulocyte count = 15.7%) had a higher MCH (33.0 +/- 1.8 mu microgram) and larger MCV (97 +/- 5.3 cu micrometers). These data indicate that Hb SS disease is associated with "relative microcytosis," presumably a consequence of reduced hemoglobin production.