XXXXY Variation of Kleinfelter's Syndrome
49,XXXXY.  This karyotype shows a variant of Klinefelter's syndrome. Individuals with this syndrome are male, typically with the karyotype 47,XXY. They exhibit a characteristic phenotype including tall stature, infertility, gynecomastia and hypogonadism. Aneuploidy above one extra chromosome is usually fatal but because of X-inactivation, which "turns off" all but one X chromosome per cell, the effects of 3 extra chromosomes are reduced.

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Image from UW Pathology Cytogenetics Gallery