Distinct mechanism of formation of the 48, XXYY karyotype.

BACKGROUND: To expose the unusual nature of a coincident sex chromosomal aneuploidy in a patient and his father. Molecular mechanisms involved probably are based on the sperm chromosome of paternal origin, which determine the mode of formation. Conventional cytogenetics techniques and multiple Quantitative Fluorescent PCR of STR markers in sexual chromosomes in the patient and his parents.

RESULTS: 48,XXYY and 47,XYY aneuploidies in the patient and his father, respectively, were identified. The additional X and Y chromosomes showed parental origin.

CONCLUSIONS: An infrequent origin of the 48,XXYY syndrome was demonstrated. Mostly, it is thought to result from an aneuploid sperm produced through two consecutive non disjunction events in both meiosis I and II in a chromosomally normal father, but in our father's patient a 47,XYY was discovered. It is suggested that a higher incidence of 24,XY and 24,YY sperm may be possible in 47,XYY individuals andan increased risk for aneuploidy pregnancies may exist. Although 48,XXYY patients and Klinefelter syndrome are often compared, recently they are regarded as a distinct genetic and clinical entity.