[Low stature in males with normal phenotype and 45,X/46,XY mosaicism]

There is wide variation in the clinical expression of 45,X/46,XY mosaicism. Ninety percent of prenatally diagnosed boys have normal male phenotype at birth, while those diagnosed postnatally show a wide spectrum of phenotypes, ranging from Turner syndrome, mixed gonadal dysgenesis, and male pseudohermaphroditism to apparent normality. We report the clinical, cytogenetic, endocrinologic and histologic findings in three boys with an apparently normal male phenotype and 45,X/46,XY mosaicism who were diagnosed postnatally because of their short stature. With the exception of one patient with Turner stigmata, no other abnormal features were found. No correlation between the proportion of 45,X/46,XY cell lines in blood, gonads and phenotype was found. Both prenatally and postnatally diagnosed boys with normal male phenotype must be followed-up because they can develop late-onset abnormalities, such as dysgenetic testes leading to infertility or neoplastic transformation, and short stature, which could be improved with growth hormone therapy.