Simplistically, the cause of the gender ambiguity is an excess of androgen. More than 95% are due to CAH, with the remainder resulting from maternal androgen exposure. These patients have a typical female Müllerian ductal system with an upper vagina, uterus, and fallopian tubes (see Table 60.1 ). They also have normal regression of the Wolffian ducts. The level of virilization depends largely on the timing and magnitude of androgen exposure to the external genitalia. The phenotype can range from mild clitoromegaly to a typical male appearance.

Virilization in CAH is due to the inability of the adrenal gland to form cortisol. The precursors above the enzymatic defect are shunted into the mineralocorticoid or sex-steroid pathways. Also, the end products generally have some, albeit weak, glucocorticoid function. The lack of cortisol for negative feedback inhibition of adrenocorticotropic hormone (ACTH) production by the pituitary leaves this pathway unchecked. Excess androgen is produced and is responsible for the virilization. The corticosteroid synthetic and alternative pathways are shown in Fig. 60.2 . The most common form of CAH is 21-hydroxylase deficiency ( 21-OHD ), which accounts for more than 90% of CAH. The 21-OHD gene has been mapped to the short arm of chromosome 6. The variable location of the adrenal defect and relative function of the gene results in salt-wasting and nonsalt-wasting forms. Type 1 results in virilization but no salt wasting. The gene defect affects only the fasciculata zone of the adrenal, and results in blocking cortisol production. However, the gene is normally expressed in the glomerulosa zone with preservation of mineralocorticoid production. In type 2, also called the classic type, the gene abnormality affects both adrenal zones. Salt wasting results in dehydration and/or vascular collapse, and hyperkalemia develops because of the block in mineralocorticoid production.

Pathways of steroid biosynthesis. The numbers correspond to CAH type and the location of the enzyme defect (see the text).

11β-Hydroxylase deficiency, type 3, is a less common cause of CAH. This gene has been mapped to the long arm of chromosome 8. This abnormality results in virilization associated with hypertension due to the synthetic block being below deoxycorticosterone (DOC). DOC has potent mineralocorticoid function resulting in sodium resorption, fluid overload, hypertension, and hypokalemic acidosis. Finally, type 4 is an extremely rare form of CAH resulting from 3β-hydroxylase deficiency with severe salt wasting and typically early death. It is the only type of CAH that can cause gender ambiguity in males and females.

Virilization of the female fetus can also be caused by exogenous androgen exposure from the mother. This occurs primarily with the use of progesterone, commonly used as an adjunct to assist with fertility and in vitro fertilization. Endogenous androgen exposure due to virilizing maternal ovarian tumors has also been reported; however, these tumors are usually virilizing to the mother, with the fetus being unaffected.

The diagnosis of CAH is based on the previously described clinical and electrolyte abnormalities in addition to elevated 17-hydroxyprogesterone (17-OHP) levels. Newborn screening has included assessment of 17-OHP levels for over 20 years in the United States. This screening test detects salt wasting forms of 21-OHD to expedite diagnosis and critical treatment. DOC and deoxycortisol levels also aid in determining which specific enzymatic defect is present. The physical examination is notable for the absence of palpable gonads, varying degrees of virilization of the clitoris, and bronzing of the skin. Palpation of a gonad virtually excludes the diagnosis of 46,XX DSD. The genitogram and an ultrasound (US) study mirror these findings, revealing Müllerian structures with a variable-length urogenital sinus.

As all forms of CAH are inherited in an autosomal recessive manner, genetic counseling is recommended. Families with a known history of CAH should consider maternal treatment with dexamethasone before week 10 of gestation to eliminate or improve the level of fetal virilization. Postnatally, cortisol replacement with hydrocortisone is the mainstay of therapy, with the addition of fluorhydrocortisone if salt wasting is present. Supportive management of fluid and electrolyte abnormalities is best provided in a neonatal intensive care unit.

With regard to gender identity, the vast majority of patients with CAH (∼95%) identify as female and female gender assignment is generally given for the 46,XX karyotype. The ovarian function is no different than a non-CAH patient with regards to endogenous hormone production and fertility potential. If surgical reconstruction is needed, the feminizing genitoplasty may include some or all of the following: clitoroplasty, monsplasty, vaginoplasty, and urogenital sinus mobilization.

Mullerian agenesis (Mayer–Rokitansky–Küster–Hauser syndrome) is characterized by a 46,XX karyotype with normal female external genitalia but a short, blind-ending vagina. Normal ovaries and fallopian tubes are present, but the uterus is generally rudimentary. Patients are seen initially with primary amenorrhea but may have cyclical pelvic pain if there is any functioning endometrium. Treatment is geared toward vaginal reconstruction to allow menses or intercourse, or both. Mullerian and renal development are closely related and thus when a Mullerian anomaly is found renal anomalies should also be ruled out. MURCS is a syndrome including Mullerian agenesis, renal agenesis, and cervicothoracic somite dysplasia.

The androgen deficit may result from a defect in synthesis. Several rare adrenal enzyme deficiencies have been implicated, including 3β-hydroxylase, 17α-hydroxylase, and 20,22-desmolase. All are involved in the steps from cholesterol to androstenedione and testosterone and are associated with severe CAH and often death. 3β-Hydroxylase and 20,22-desmolase deficiencies are associated with cortisol and aldosterone deficits with hyponatremia, hyperkalemia, and metabolic acidosis. In 17α-hydroxylase deficiency, mineralocorticoid production is preserved, resulting in excess salt and water retention, hypertension, and hypokalemia. In the male the phenotype is variable, ranging from the appearance of a proximal hypospadias with cryptorchidism to that of a phenotypic female with a blind-ending vagina.

M üllerian -I nhibitory S ubstance D eficiency

MIS is produced by the Sertoli cells in the testis and causes regression of the Müllerian ductal structures. In this rare syndrome of abnormal MIS production or MIS-receptor abnormality, Wolffian ductal development is unimpaired, but the Müllerian ducts also persist. Because the infant has a typical male phenotype, this syndrome is rarely encountered in the neonatal period. The most common presentation to the surgeon is that of finding a fallopian tube adjacent to an undescended testis in the hernia sac at the time of orchiopexy, which is what influenced the former terminology of “hernia uterine inguinale.”

If this scenario is encountered, a biopsy of the gonad should be performed, the hernia should be repaired, and all structures left intact until completion of a full evaluation with karyotype and MIS levels. Apparent males can also present with bilateral nonpalpable testes, and Müllerian structures are found at laparoscopy ( Fig. 60.3 ). Abnormal MIS-receptor gene assays can also be helpful for verifying the diagnosis in those with a normal MIS level. Subsequent management is primarily orchiopexy. However, this can be difficult because the vas deferens can be closely adherent or ectopic to the fallopian tube or uterus. Excision of discordant ductal structures can be attempted but given the relatively low risk associated with leaving these structures, the risk of damage to the vas during this dissection outweighs the benefit of removal. Despite normal testosterone levels, the patient often has impaired spermatogenesis.

A 2-year-old boy presented with nonpalpable testes. A karyotype showed XY. (A) External genitalia were male. (B) Laparoscopy revealed bilateral gonads that were testes on longitudinal biopsy. Müllerian structures ( arrows ) were also seen. Note the rudimentary uterus (being held by the grasping forceps). This patient had abnormal Müllerian-inhibitory substance receptor function.

Defects in 17,20-desmolase and 17β-hydroxysteroid oxidoreductase act at the testicular level to convert androstenedione to testosterone. Because the adrenal is unaffected, CAH does not occur. The phenotype can be quite variable, but those with complete feminization can escape detection at birth and be raised as females. Progressive virilization is related to excess gonadotropin production at puberty, which may partially compensate for the lack of testosterone synthesis. Phallic growth and the development of male secondary sex characteristics create a conundrum regarding gender reassignment when the diagnosis is made later in life.

Despite adequate production of androgen, receptor defects can render cells blind to the virilizing effects of the hormone. The phenotype is variable and depends on the degree of insensitivity of the receptor for androgen.

Ovotesticular DSD exists when both ovarian and testicular tissue are present. The gonadal configuration can also be quite variable, with the ovary/ovotestis combination being most common in the United States, but any combination can occur. Ovotestes are usually polar, with an ovary at one end and a testis at the other, but the distribution can be longitudinal, requiring deep longitudinal biopsy to adequately sample the gonad. Because of the paracrine effect of the gonad, the ipsilateral internal duct structures correlate with the type of gonad present. Ovotestes are associated with a variable duct structure, but usually fallopian tubes prevail. A decisively Müllerian or Wolffian duct structure is usually found rather than an ipsilateral combination.

Ovotesticular DSD can be associated with a variety of karyotypes, with 46,XX being the most common, but different chromosomal content has been correlated with different races. It is thought that a translocation of the SRY gene or associated genes to an X chromosome or autosome explains the development of testicular tissue in the 46,XX karyotype. It is more difficult to explain ovarian tissue in a patient with a 46,XY karyotype. Likely, key genes in ovarian development are present, but undetected, and complement the normal X chromosomal content. An unappreciated mosaicism could also have occurred.

The phenotype covers the entire spectrum, with ambiguity and asymmetry being the rule, but with a tendency toward virilization. Although it is unusual for ovaries to be found in the labioscrotum, testes and ovotestes are often palpable. Fertility has been described in those raised as female, but testicular fibrosis makes it unlikely in those raised as male. ^,

Mixed gonadal dysgenesis (MGD) is the second most common form of neonatal ambiguous genitalia. The patient will have a testis on one side and a dysgenetic gonad on the other, characterized microscopically by normal ovarian stroma without oocytes ( Fig. 60.4 ). The internal duct structure mirrors the ipsilateral gonad, with the dysgenetic gonad associated with a fallopian tube and uterus resulting from the lack of MIS. The karyotype is generally a mosaic of 45,XO/46,XY, and the stigmata of Turner syndrome are variably present. The phenotype is ambiguous, but virilized, and the testis is usually undescended.

Mixed gonadal dysgenesis. The left testis was descended, and the right dysgenetic gonad was intraabdominal. F, Fallopian tube; S, dysgenetic gonad; T, testis.

Photo taken from foot of table.

The risk of a gonadal tumor, usually gonadoblastoma, is as high as 20%, and tumors can develop in either the testis or dysgenetic gonad. This may be mediated by the TSPY gene on the Y chromosome. An increased risk of Wilms tumor also is present in MGD. The Denys–Drash syndrome occurs in approximately 5% of patients with MGD and is classically described as ambiguous genitalia, Wilms tumor, and glomerulopathy, which is often associated with hypertension.

The diagnosis is suggested by the physical stigmata of Turner syndrome on examination (webbed neck, shield chest) and 45,XO/46,XY karyotype. However, the finding of a testis and dysgenetic gonad confirms the diagnosis. Historically, most patients with MGD have been raised as females because of the short stature conferred by Turner syndrome and the malignant risk of the retained testis. Females undergo early gonadectomy and feminizing genitoplasty. Males require early excision of the dysgenetic gonad, orchiectomy if raised as female, or orchiopexy of the testicle and hypospadias repair if raised as male. Infertility is the rule despite adequate testicular endocrine function. Because of the increasing awareness regarding testosterone imprinting on the brain, more masculinized patients are being raised as males. If individuals are raised as male and one testicle is left in place, close surveillance of the testis is necessary, unless elective orchiectomy and hormone replacement are chosen. Testicular biopsy at the time of puberty to exclude dysgenetic elements has been recommended. If carcinoma in situ is identified, low-dose radiation therapy is curative.

Pure gonadal dysgenesis (PGD) is characterized by dysgenetic gonads bilaterally. The external phenotype and internal duct structures are female. These patients are generally seen at puberty with primary amenorrhea. The chromosomal makeup is classically 46,XX. PGD is an autosomal recessive trait, so genetic counseling is warranted. This implies that the condition can be caused by abnormalities in the X chromosome or supporting autosomal genes involved in gender differentiation. The gonads do not carry risk of malignant degeneration.

Other conditions are also closely related to bilateral dysgenetic gonads. The chromosomal makeup is quite variable and can be 46,XY (XY sex reversal, Swyer syndrome, or male Turner syndrome), 45,XO, or a mosaic. Variants with a Y chromosome differ in that they carry a high rate of malignancy in the retained dysgenetic gonads. The phenotype is as described earlier, but these patients may be first seen in infancy with gonadoblastomas or dysgerminomas or with germ cell tumors that become more common in adolescence. Multiple chromosomal deletions and mutations have been described causing this syndrome. The finding of a female external phenotype and an internal duct structure with bilateral dysgenetic gonads confirms the diagnosis. Follicle-stimulating hormone and LH levels are generally elevated, and estrogen and testosterone levels are decreased. The diagnosis may be suggested by the physical stigmata of Turner syndrome. In classic 46,XX PGD, the gonads can be left because there is no malignant potential. If a Y chromosome is present, gonadectomy should be performed, as there is a higher incidence of malignancy. In either case, hormonal replacement at puberty is required because the dysgenetic gonads do not provide any endocrine function.

Several syndromes do not fit neatly into the described classification systems. Bilateral vanishing testis syndrome is characterized by a 46,XY karyotype but absent testes. This generally results in virilization to the point of normal external genitalia and internal duct structure but absent testes. The testes were thought to have produced androgen at some point, resulting in masculinization, but subsequently vanished related to torsion or regression. Patients are generally raised as boys, and hormonal supplementation at puberty is required.

Klinefelter syndrome is characterized by a male karyotype containing two or more X chromosomes (47,XXY, 48,XXXY, etc.). Although phenotypically male prepubertally, these patients acquire abnormal male secondary sexual characteristics (tall stature with disproportionately long legs, sparse facial hair, decreased muscle mass, and a feminine fat distribution), and infertility. The testes are small and hard, with decreased androgen production and elevated estradiol levels related to primary hypergonadotropic hypogonadism. Gynecomastia often occurs with an increased risk of breast cancer. Fertility has been reported but requires assisted means, such as intracytoplasmic sperm injection (ICSI).

46,XX testicular DSD (XX sex reversal) is characterized by a male phenotype with a 46,XX karyotype. Most commonly, this occurs from translocation of Y chromosomal material to the X chromosome, but it also can occur from mutation of the X chromosome or from mosaicism. The phenotype and management are similar to those of Klinefelter syndrome, with the exception of shorter stature.