Concurrence of fragile X and Klinefelter syndromes: report of a new case of paternal nondisjunction.

The concurrence of fragile X and Klinefelter syndromes would be expected occasionally. Therefore, the analysis of the literature showed that the concurrence of both conditions was found at least 16 times. Among them, only seven cases were analyzed for the parental origin of the extra chromosome X, suggesting that the maternal nondisjunction was preferentially inherited. We present the third patient with the concurrence of fragile X and Klinefelter syndromes, in which the parental origin of the supernumerary chromosome X was paternal. This finding reinforces that the parent-of-origin predisposition of the concurrence of the fragile X and Klinefelter syndromes is a pure coincidence.