A blood film from a patient is reported as showing a “dimorphic population of red cells”.
a) What is meant by dimorphic population?
b) Give four causes of this picture.
Dimorphic population of red cells is the presence of two or more morphologically distinct red cell populations in the same bloodstream. This is a finding usually reported on the basis of a strongly bimodal red cell volume histogram which is produced by automated blood cell analysers (Constantino, 2011). The term is somewhat misleading, as the histogram may have more than two discrete red cell populations sharing the bloodstream. However, usually there's only two cell populations; typically a group from before some sort of illness or treatment, and a group from after that event. Examples include:
Following from this, numerous possibilities exist to explain the concurrent presence of several morphologically distinct red cell variants, some of which are totally predictable. This representative list is cut-and-pasted from Constantino (2011):
Constantino, Benie T. "The red cell histogram and the dimorphic red cell population." Laboratory Medicine 42.5 (2011): 300-308.