An individual with normal male habitus, body proportions, and secondary sexual characteristics was admitted to the hospital with head trauma. A routine blood smear demonstrated that 36% of the granulocytes had “drumsticks.” Chromosomal analysis revealed a 46, XYqh+ karyotype. The extremely large Y chromosome was located by quinacrine fluorescence in the “drumstick” of the polymorphonuclear granulocytes. The presence of a large Y chromosome may thus produce pseudo‐drumsticks. Fluorescent staining can distinguish between true drumsticks bearing the inactive X of normal females and the pseudo‐drumsticks in a normal male produced by a large Y chromosome.
- chromosome polymorphism
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