Clinical characteristics: Nonsyndromic disorders of testicular development are a group of conditions characterized by the following:
A generally normal physical examination with absence of clinical findings involving organ systems other than the reproductive organs
A normal 46,XY karyotype by conventional staining
External genitalia that range from ambiguous to normal female
Internal genitalia that range from absent müllerian structures to a fully developed uterus and fallopian tubes
Gonads that are characterized as normal testis, ovotestis, dysgenetic testis, or streak
Based on the particular features seen in any given individual, the clinical diagnosis may be designated as 46,XY disorder of sex development (DSD) or 46,XY complete gonadal dysgenesis (CGD).
Diagnosis/testing: Nonsyndromic 46,XY DSD and 46,XY CGD must be distinguished from syndromic forms, in which additional organ systems, growth, and cognitive development may also be affected. Biallelic pathogenic variants in DHH, heterozygous pathogenic variants in MAP3K1 and NR5A1, hemizygous pathogenic variants in SRY, hemizygous duplication of NR0B1, and heterozygous deletion of DMRT1 are causative of nonsyndromic 46,XY disorders of testicular development.
Genetic counseling: Nonsyndromic disorders of testicular development can be inherited in a sex-limited autosomal recessive (DHH), sex-limited autosomal dominant (MAP3K1, NR5A1, and heterozygous deletion of DMRT1), Y-linked (SRY), or X-linked manner (hemizygous duplication of NR0B1). Genetic counseling and risk assessment depend on determination of the specific cause and the sex chromosome complement of the individual who harbors the pathogenic variant(s).
Management: Treatment of manifestations: Evaluation and long-term management is best performed at a center with an interdisciplinary care team (including clinical geneticists, endocrinologists, surgeons, and mental health professionals) experienced in the diagnosis and management of DSD; all individuals should receive a sex of rearing; surgical decisions should be made after detailed discussion with the family regarding risks, benefits, and limitations of any proposed surgery; surgical intervention (hypospadias repair, orchiopexy, scrotoplasty, and phalloplasty in males and clitoroplasty, vaginoplasty, and urogenital sinus mobilization in females) should focus on functionality; whenever possible, removal of tissue and irreversible procedures should be avoided; streak gonads and nonfunctional dysgenetic gonads should be removed to decrease the risk for gonadoblastoma; dysgenetic gonads with residual function that are not removed require tumor surveillance; if gonads are retained, surveillance for the development of contrasexual puberty is warranted if sex of rearing is discordant with gonadal sex; sex steroid therapy (testosterone in males and estrogen or estrogen/progesterone in females) is important for the development of secondary sexual characteristics and for normal adolescent bone mass accrual; 46,XY individuals with a heterozygous pathogenic variant in NR5A1 should be monitored for adrenal insufficiency; most affected individuals are infertile, although assisted reproductive technologies may help achieve pregnancy in some cases.
Surveillance: Regular follow up with an interdisciplinary DSD team including endocrinology, genetics, obstetrics/gynecology, psychology, and urology.
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