Sample Question from Variations in White Cell Morphology - Granulocytes, presented by MediaLab

Nuclear Variations

Barr Body

A Barr body appears as a small drumstick-like projection on one of the lobes of a some of the neutrophil in females. Barr bodies are attached to the nuclear lobe by a single narrow stalk which distinguishes them from other thicker projections, sometimes referred to as "clubs."
Clubs have a thicker, and sometimes, a double stalk. This projection can be seen in both males and females and has no clinical significance.
Barr bodies must also be distinguished from hair-like projections sometimes seen in the band form, following irradiation or in patients with a malignant tumor that has metastasized.
Since Barr bodies are the morphological expression of the inactivated X chromosome, one Barr body can be seen in up to 3% of the neutrophils on a female's peripheral blood slide. In rare chromosome disorders in which three or more X chromosomes are present, two to three Barr bodies per neutrophil can be seen.
Recognition of a Barr body in a neutrophil is important in order to avoid reporting it as abnormal unless two or more per neutrophil are seen.

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