Identification of an AR mutation in Klinefelter syndrome during evaluation for penoscrotal hypospadias

Genital anomalies, ranging from female genitalia to milder degrees of undervirilization, are rarely reported in Klinefelter syndrome, in which a male is classically expected to be born with male external genitalia. Though androgen insensitivity syndrome (AIS) is one of the possible pathogenic mechanisms also in Klinefelter syndrome with genital anomalies, to date the AR gene has not been analyzed in any of the published cases of Klinefelter syndrome of the milder phenotype, except for those patients presenting with a severe phenotype, such as female external genitalia.Lack of interest in considering androgen insensitivity in Klinefelter syndrome with a milder phenotype of genital anomalies may impede its identification through an accurate diagnosis. We present a 14-month-old boy with penoscrotal hypospadias, micropenis, and a ventral penile chordee abnormality who was observed to have both a 47,XXY karyotype and a known missense mutation in the ARgene that was inherited from his mother. Although it is recommended that Klinefelter syndrome be considered in the differential diagnosis of penoscrotal abnormalities, mutations in specific genes involved in androgen synthesis or responsiveness should also be investigated.