Evaluation of the infant with ambiguous genitalia

Evaluation of the infant with ambiguous genitalia

• discrepancy between external genitalia, gonadal and chromosomal sex are classified as having a disorder of sex development

• "disorders of sex development" (DSD) Manifestations may include:

• bilateral cryptorchidism• perineal hypospadias with bifid scrotum• clitoromegaly• posterior labial fusion• phenotypic female appearance with a palpable gonad • hypospadias and unilateral nonpalpable gonad

DSDs also include infants with discordant genitalia and sex chromosomes

• Turner syndrome (45,XO) and Klinefelter syndrome

• 46,XY infants with palpable gonads and simple hypospadias or microphallus, although undervirilized, do not have truly ambiguous genitalia

NORMAL SEX DEVELOPMENT

• Before 7 week both XX and XY fetuses have similar reproductive structure

• After 7 week, fetuses bearing a Y chromosome begin developing testes,

• thereby becoming sexually distinct from fetuses without a Y chromosome.

• ovarian development also requires active genetic pathways

• gonadal differentiation and function determines the genital phenotype.

Multiple genes contribute to normal sexual differentiation

• mutations in these genes can lead to various DSDs :• Genes involved in gonadal development• SRY • SOX9• SF-1• DHH• DAX-1• WT-1• WAGR syndrome• Denys-Drash syndrome• Frasier syndrome

Internal genitalia

• Wolffian (mesonephric) and Müllerian (paramesonephric) ducts develop in both sexes

• In males, at approximately the seventh week of gestation, testicular Sertoli cells begin secreting Müllerian-inhibiting substance (MIS, also called Müllerian-inhibiting hormone, and AMH, anti-Müllerian hormone), which induces Müllerian duct regression [ 19 ].

• In females, the lack of testosterone leads to Wolffian duct regression and, in response to the lack of MIS, permits Müllerian duct maturation into oviduct, uterus, cervix, and upper vagina,

External genitalia

• The external genitalia become sexually distinct at approximately the ninth week of gestation, after Leydig cells have produced sufficient testosterone to permit peripheral synthesis of DHT

• 46,XY infants who lack 5-alpha-reductase type 2 are born with normally functioning testes but undervirilized external genitalia.

• Male external genital morphogenesis is complete by 12 to 16 weeks

• By 12 weeks, the non-hormone-dependent separation of vagina and urethra is complete in females

• Excess androgen exposure before this separation can cause labial fusion and development of a phallic urethra or urogenital sinus, but later exposure causes only clitoral enlargement and masculinization/scrotalization of labial folds.

CLINICAL FEATURES

• Penile length:In a term infant, at birth, the normal penile length is ≥2.5 cm, and normal penile diameter is ≥0.9 cm

• (micropenis) may be caused by decreased testosterone/DHT exposure in the second or third trimester and by deficiencies of growth hormone or gonadotropin.

• Gonads : presence and position of the gonads• In a 46,XY child, bilateral nonpalpable testes may arise from

isolated cryptorchidism, anorchia, or occur in conjunction with persistent Müllerian duct syndrome. In a 46,XX child, virilizing congenital adrenal hyperplasia (CAH) should be ruled out.

• Gonads palpable below the inguinal ligament (eg, in the labioscrotal folds) ( picture 5 ) are usually testes

• Asymmetry of the gonads or other genitalia may indicate gonadal dysgenesis or development of both gonadal structures namely ovary and testis, termed ovotesticular DSD

• Urethral opening; A single opening at the base of the phallus :

• an incompletely fused penile urethra• a virilized urogenital sinus• these findings must be confirmed either

bycystoscopy/vaginoscopy or radiographically,

• Clitoral size:Normal clitoral width in a neonate ranges from 2 to 6 mm.

• lengths of more than 9 mm are unusual in normal infants

Virilization :Female virilization standards for CAH have been established by Prader based upon the degree of virilization of the urogenital sinus and the external genitalia

For assessing the development of external genitalia in 46,XY children with DSD, the Quigley scales have been widely used

• Anogenital ratio:is independent of gestational age and body size

• distance between the anus and posterior fourchette divided by the distance between the anus and the base of the clitoris [ 29 ].

• A ratio of >0.5 suggests virilization with some posterior labial fusion.

DIAGNOSTIC APPROACH• A diagnosis of a disorder of sex development (DSD) should be considered

in infants who have:• Bilaterally nonpalpable testes ( picture 1 ).• Microphallus (stretched penile length less than 2.5 cm in a full-term

infant); microphallus without associated hypospadias is not "ambiguous," but may be a marker of other disorders.

• Perineal hypospadias with bifid scrotum ( picture 2 ).• Clitoromegaly (clitoral width >6 mm or clitoral length >9 mm) (

picture 3A-B ).• Posterior labial fusion (anogenital ratio >0.5) ( picture 4 ). • Gonads palpable in the labioscrotal folds ( picture 5 ).• Hypospadias and unilateral nonpalpable gonad ( picture 6A-B ).• Discordant genitalia and sex chromosomes ( picture 7 ).

INITIAL EVALUATION• History:• Prenatal exposure to androgens (eg, progesterones, danazol ,

testosterone) or endocrine disrupters ( phenytoin , aminoglutethimide).

• Maternal virilization in pregnancy (placental aromatase deficiency, luteoma).

• Family history of females who are childless or have amenorrhea (androgen insensitivity).

• Family history of unexplained infant deaths (congenital adrenal hyperplasia).

• History of consanguinity (or homogeneous population) (recessive disorders, eg, CAH or disorders of androgen biosynthesis). (See "Diagnosis and treatment of disorders of the androgen receptor" .)

INITIAL EVALUATION

• Physical examination:• inspection and palpation of the genitalia• associated nongenital anomalies or dysmorphic

features should be documented • Infants with congenital gonadotropin-releasing

hormone deficiency also may have cleft lip or palate and other midline defects

• Infants with Smith-Lemli-Opitz syndrome• Individuals with P450 oxidoreductase deficiency

Laboratory tests

• determination of sex chromosomes and assessment of gonadal and adrenal steroids.

• • karyotype:peripheral leukocytes, gonadal tissue • Based on karyotype classification of the infant

into:• XX DSD• XY DSD• Mixed sex chromosome DSD

• 17-hydroxyprogesterone should be measured promptly in all infants with nonpalpable gonads

• serum electrolytes• Next, evaluation for the SRY gene• All infants with ambiguous genitalia should also be tested

for less common types of CAH• Measurement of cortisol and ACTH• measurement of Müllerian inhibiting substance (MIS) or

inhibin B and the testosterone response to administration of hCG

• FISH probe for the SRY gene

Imaging

• Ultrasonography of the abdomen and pelvis• Retrograde urethrogram • cystoscopy/vaginoscopy• laparoscopic visualization with gonadal biopsy

46 XX DSD

• differential diagnosis:• (CAH) 21-alpha-hydroxylase (CYP21A2) ,11-beta-

hydroxylase deficiencies and 3-beta-hydroxysteroid dehydrogenase deficiency

• gestational hyperandrogenism, XX virilization, with normal female internal anatomy Causes include maternal luteoma or theca-lutein cysts, and placental aromatase enzyme deficiency.

• testicular DSD, • ovotesticular DSD• Other causes:SRY translocation, SOX9 duplication

Algorithm for evaluation of an infant with ambiguous genitalia and a 46,XX karyotype (SRY-negative)*