Hypersegmented neutrophils are a feature of: September 2011, March 2013

Ans. C: Megaloblastic anemia The diagnosis of vitamin B12 deficiency anemia is based on leucopenia with hypersegmented granulocytes, a moderate to severe Megaloblastic anemia, elevated levels of homocysteine and methylmalonic acid in the serum and low serum vitamin B12. Hypersegmented neutrophil Normally, the number of segments in the nucleus of a neutrophil increases as it matures and ages, after being released into the blood from the bone marrow. Whereas normal neutrophils only contain three or four nuclear lobes (the "segments"), hypersegmented neutrophils contain five or more lobes. Hypersegmented neutrophils have classically been thought to be pathognomonic of the megaloblastic anemias (anemias caused by failure of bone marrow blood-forming cells to make DNA, often caused by vitamin B12 or folate deficiencies, or DNA-replication poisons). One of the earliest, notable changes in the peripheral blood in megaloblastic processes is the appearance of hypersegmented neutrophils. Because of the sho life-span of neutrophils, these abnormal hypersegmented neutrophils characteristically appear even before the onset of anemia in megaloblastic processes. Such neutrophils are less often seen in the other classes of anemia, which together are far more common than megaloblastic types of anemia. Note that pernicious anemia is a type of megaloblastic anemia, and as such, is expected to show hypersegmented neutrophils.