The clinical significance of macrocytosis.

The cause of macrocytosis (mean corpuscular volume (MCV) greater than or equal to 105 fl) was investigated over a period of 16 months in the 70 known cases of +/- 4000 patients seen by the Department of Internal Medicine. By means of simple laboratory investigations the cause of elevated MCV was found in more than 90% of the cases. We found vitamin B12 or folic acid deficiency in 27 patients, alcohol abuse in 18, chronic persistent hepatitis in 2, hematological (pre-) malignancy in 9, hemolysis in 4, hypothyroidism in 2, and a drug effect in one patient. In 6 cases the elevated MCV could not be explained. Macrocytosis, a frequent finding that is not related to the hemoglobin concentration, is an indicator of serious pathology. The MCV level can be used to differentiate between the diagnostic categories. Only 21 patients (30%) had megaloblastic erythropoiesis that was difficult to recognize in the peripheral blood. Among the findings at routine laboratory investigations an elevated MCV may be the only indicator of vitamin deficiency, preleukemia or alcoholism.