Down syndrome and Klinefelter syndrome in the same patient. Report of a case.

A case is reported in which a patient with Down syndrome was found to also have Klinefelter syndrome. At evaluation at eight months of age, a dysmorphic syndrome suggestive of Down syndrome and severe developmental delay were present. The karyotype showed not only 21-trisomy but also XXY aneuploidy. The association of these two aneuploidies occurs more often than predicted by chance alone. Routine karyotype studies in parents and children would perhaps provide the explanation to this.