Congenital Neutropenia: How Low?

To the Editor.—  The recent article by Reed and Diehl¹ shows clearly the difference in mean corpuscular volume (MCV) between white and black volunteer soldiers and notes the historical 7% to 8% incidence of heterozygous α and β-thalassemia in blacks. However, α-thalassemia is by far the most common in blacks, and most cases are α₂- (one-deletion) thalassemia. These patients do not have an average MCV in the low seventies, but in the low eighties.^2,3 This explains the most striking feature in the MCV data provided by Reed and Diehl. There is a skew of the gaussian curve of MCV in the low eighties for black men and women, and not for white ones. Thus, their data in blacks are trimodal: the main peak with a mode of about 90 fL; the skew that probably represents 5% to 6% with α2-thalassemia and a mode of about 82 fL;