What is the role of alcohol and substance abuse in the etiology of macrocytosis?

Updated: Dec 16, 2020
  • Author: Vincent E Herrin, MD, FACP; Chief Editor: Emmanuel C Besa, MD  more...
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Long-term alcohol abuse can result in macrocytosis through a direct effect on bone marrow. This effect is not related to the presence of liver disease or vitamin deficiency and resolves only after months of abstinence from alcohol. In addition,alcohol abusers may have secondary megaloblastosis from vitamin B12 and folate deficiency due to poor nutritional intake.

Heroin users have been found to have rates of macrocytosis 5 to 10 times higher than those in the general population. However, a study of 958 patients with a heroin use disorder entering methadone maintenance treatment found that high rates of comorbid alcohol use were more likely to be the cause of macrocytosis in this population. [16]

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