The objective of this study was to describe the change in diagnosis and prognosis of a child with testicular dysgenesis and 46,XY karyotype after detection of a 45,X cell line and to discuss the difficulties caused by the terms mixed gonadal dysgenesis (MGD) and XY partial gonadal dysgenesis (XYPGD). One case was reported including clinical and laboratory findings of a child of 41-day-old infant with 1.3-cm phallus, penoscrotal hypospadias and left prepubertal testis. Karyotype 46,XY (16 cells), normal hormone levels. Right streak gonad, epididymis and müllerian remnants were removed; initial diagnosis was XYPGD. Persistent growth retardation led to further cytogenetic analysis (50 cells) and detection of a 45,X cell line. Detection of a 45,X lineage changed both the diagnosis to MGD and also the prognosis.The number of cells analyzed in karyotyping is critical. Use of MGD and XYPGD to designate both a histological picture and a syndromic diagnosis, results in lack of emphasis on clinical differences between 46,XY and 45,X/46,XY subjects.
