Rudimentary testes syndrome revisited

Sixteen children who were one day to 9 years of age underwent clinical, anatomic, and hormonal study because of extreme hypoplasia of the phallus and small testes associated with normal 46XY male karyotype. Two of them were first cousins. All patients had Leydig cell deficiency. Among 15 patients who received luteinizing hormone-releasing hormone stimulation during childhood, 11 had an exaggerated response of either one or both gonadotropins. Bilateral biopsy, performed in eight patients, showed a clearly testicular structure with either scant or incompletely differentiated tubules. These characteristics allow clear differentiation from chromosomal abnormalities and malformation syndromes. It is more difficult to differentiate between rudimentary testes and primary gonadotropic deficiencies and may not be possible until the child has reached adolescence. The syndrome of rudimentary testes may be a manifestation of XY primary gonadal dysplasia, along with pure XY gonadal dysgenesis, XY hermaphroditism, XY mixed gonadal dysgenesis, and congenital anorchia, probably resulting from fetal regression of the testes. The observed familial occurrence of the syndrome of rudimentary testes, as well as of XY gonadal dysgenesis, leads to speculation about the possibility of X-linked transmission.