Klinefelter's syndrome in identical twins with the 46,XX chromosome constitution

Abstract

Two monozygotic twins with male phenotype had a 46,XX karyotype in the buccal mucosa, blood, skin and testis. The data in fourteen previously described phenotypic males with the 46,XX karyotype are reviewed. Although they resemble patients with classic (47,XXY) Klinefelter's syndrome they tend to be better virilized and often have less severe seminiferous tubular damage. Quinacrine staining of interphase and metaphase nuclei of various tissues failed to demonstrate the presence of a Y chromosome. The reason for the development of testicular structures and a male phenotype in these patients remains speculative.