Use of a probe for the putative sex determining gene, zinc finger Y, in the study of patients with ambiguous genitalia and XY gonadal dysgenesis

Molecular and clinical studies of three cases of female pseudohermaphroditism with caudal dysplasia suggest multiple etiologies

Female pseudohermaphroditism with caudal dysplasia is a clinical entity in which normal-appearing male genitalia may occur in the apparent absence of testosterone or the sex-determining gene (SR Y). We have extended observations of two previously reported cases, and report a third case, which strongly suggests multiple etiologies. The first case was one of identical twins. The other identical twin did not show female pseudohermaphroditism with caudal dysplasia, but both patients had the rare birth defect of neonatal cataracts. We have explored skewed X-inactivation as a possible difference between the two twins, with a negative result. The second case had a deletion at 10q25.3-->ter. This is near the location of PAX2, and we searched for mutations in PAX2 in both this and the first case, with negative results. Neither patient had a scrotal raphe, suggesting that a failure of division of the cloacal membrane was an important step in their development of female pseudohermaphroditism. The final case is newly described and differed from the above two in the presence of a scrotal raphe and an elevated testosterone level. Although no source for the testosterone was found, this case suggests that the etiology in this patient was different and that the presence of a scrotal raphe can be used to distinguish between at least two etiologies.

Female pseudohermaphroditism with multiple caudal anomalies: absence of Y-specific DNA sequences as pathogenetic factors

46,XX female pseudohermaphrodites have been previously described with nearly complete masculinization of the external genitalia and no apparent source of testosterone. Multiple malformations of internal genital, urinary, and gastrointestinal tracts are associated. We have evaluated four such infants with female pseudohermaphroditism and multiple caudal anomalies. Three cases had apparently normal chromosomes (46,XX); one had a 46,XX,del(10)(q25.3-->qter) chromosome constitution. The chromosome breakpoint is in the region of PAX2, a developmentally important paired box gene which is expressed in urogenital tissue. Using the polymerase chain reaction, we screened for the presence of multiple Y specific sequences, including SRY (sex determining region, Y chromosome), that could explain masculinization of the external genitalia. All were negative for Y centromeric sequences, ZFY (Zinc finger Y), and SRY. Furthermore, there was no evidence for adrenal or other sources of testosterone. We suggest that the masculinization in these cases is the result of abnormal expression of genes which would normally be regulated by testosterone.

Genetic aspects of ambiguous genitalia

The unexpected arrival of an infant with ambiguous genitalia is stressful for both physicians and parents. Careful assessment of the external genital structures and the overall infant directs the immediate management. Investigations include evaluation of glucose, electrolytes, chromosomes, and 17-ketosteroids as well as ultrasound and evaluation of the urinary tract as appropriate. The review of family and pregnancy history addresses concerns regarding medications or previously affected infants. The most efficient method of evaluating such an infant is by a team approach, with each team member contributing expertise and one communicating with the family and the family physician. Unnecessary overlap of investigations can be avoided as well as rash decisions as to sex of rearing. Counseling the family provides support during the stressful first days until decisions can be made about information regarding the diagnosis and prognosis of the infant, recurrence risk figures for subsequent pregnancies or other family members, and whether prenatal diagnosis might be appropriate. The family can be helped to move through the ordeal with their child and develop trust in the team members.