Disorders of Sexual Development

Disorders of Sexual Development

Disorders of Sexual Development

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DSD Basics - What's in a Name?

  • Definition: Disorders of Sex Development (DSD) are congenital conditions with atypical development of chromosomal, gonadal, or anatomical sex.
  • Normal Sexual Differentiation: Key players include:
    • SRY gene: Primary testis-determining factor on Y chromosome.
    • SOX9: Testis development.
    • AMH (Anti-Müllerian Hormone): From Sertoli cells; causes Müllerian duct regression.
    • Testosterone: From Leydig cells; develops Wolffian ducts.
    • DHT (Dihydrotestosterone): From testosterone via 5α-reductase; virilizes external genitalia.

Normal Male and Female Sexual Differentiation

  • Classification:
    • Sex Chromosome DSD (e.g., Turner syndrome, Klinefelter syndrome).
    • 46,XY DSD (e.g., Androgen Insensitivity Syndrome, 5α-reductase deficiency).
    • 46,XX DSD (e.g., Congenital Adrenal Hyperplasia).

⭐ SRY gene on Y chromosome is the primary testis-determining factor.

46,XX DSD - Ovaries & Androgens

  • Ovaries present; virilization due to excess androgens.
  • Congenital Adrenal Hyperplasia (CAH): Most common cause.
    • 21-Hydroxylase Deficiency (most frequent):
      • Ambiguous genitalia in females.
      • Salt-wasting (↓aldosterone, ↑renin) in ~75%.
      • Diagnosis: ↑17-hydroxyprogesterone (17-OHP).
    • 11β-Hydroxylase Deficiency:
      • Ambiguous genitalia.
      • Hypertension (↑deoxycorticosterone).
      • Diagnosis: ↑11-deoxycortisol.
    • Management: Glucocorticoids, mineralocorticoids (if salt-wasting), surgical correction.
  • Maternal Androgen Exposure:
    • Androgen-secreting tumors (e.g., luteoma).
    • Exogenous androgens.

⭐ The most common cause of 46,XX DSD is 21-hydroxylase deficiency, leading to increased 17-hydroxyprogesterone (17-OHP).

46,XY DSD - Testes & Targets

  • 46,XY karyotype with undervirilization due to issues with testes or androgen targets.
  • Disorders of Testicular Development:
    • Gonadal dysgenesis (e.g., Swyer syndrome): Streak gonads, female phenotype.
  • Disorders of Androgen Synthesis/Action:
    • 5-alpha-reductase deficiency (5-ARD): "Guevedoces." Ambiguous genitalia at birth, virilization at puberty. ↓DHT. T/DHT ratio > 20.
    • Androgen Insensitivity Syndrome (AIS): Defective androgen receptor.
      • Complete (CAIS): Female external genitalia, absent uterus. Testes present.
      • Partial (PAIS): Ambiguous genitalia.
  • Diagnosis: Karyotype, hormones (T, DHT, LH, AMH), hCG stim test, genetics. DHT conversion in 8-week human embryo

⭐ Complete Androgen Insensitivity Syndrome (CAIS) presents with a 46,XY karyotype, female external genitalia, absent uterus, and testes producing normal testosterone.

Chromosomal DSDs - Gene Juggle

  • Turner Syndrome (45,X): Streak gonads, ovarian dysgenesis, primary amenorrhea.
  • Klinefelter Syndrome (47,XXY): Testicular dysgenesis (small testes), azoospermia, gynecomastia.
  • Ovotesticular DSD: Ovotestis (ovarian & testicular tissue); variable karyotype (46,XX; 46,XY).
  • Gonadal Dysgenesis (e.g., Swyer - 46,XY): Female phenotype, streak gonads. Classification of Disorders of Sexual Development

⭐ Swyer syndrome (46,XY pure gonadal dysgenesis): streak gonads; gonadectomy vital due to high gonadoblastoma risk.

DSD Approach - Clue Cracking Care

Newborn with ambiguous genitalia: prompt, systematic evaluation.

  • History: Maternal (drugs, virilization, family Hx DSD, consanguinity), neonatal.
  • Examination: Genital (phallus, gonads, meatus, fusion - Prader staging), dysmorphic features.
  • Initial Investigations (Key):
    • Karyotype (STAT).
    • Serum electrolytes (Na+, K+), glucose.
    • Hormones: 17-OHP, Testosterone, AMH.
    • Pelvic USG (müllerian structures, gonads).
  • Management: MDT essential. Gender assignment: complex decision (diagnosis, surgery, fertility, family values).

Newborn ambiguous genitalia diagnostic algorithm

⭐ Karyotyping is the cornerstone initial investigation in evaluating a newborn with ambiguous genitalia.

High‑Yield Points - ⚡ Biggest Takeaways

  • Karyotyping is the crucial first investigation for ambiguous genitalia.
  • CAH (21-hydroxylase deficiency) is the most common cause of 46,XX DSD virilization.
  • AIS (46,XY): female external genitalia, absent uterus, undescended testes; prophylactic gonadectomy.
  • 5α-reductase deficiency (46,XY): ambiguous genitalia at birth, virilizes at puberty.
  • Swyer Syndrome (46,XY): female, streak gonads, uterus present; high tumor risk, gonadectomy.
  • MGD (45,X/46,XY mosaicism): variable phenotype, asymmetric gonads, high tumor risk.

Practice Questions: Disorders of Sexual Development

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Which of the following is the least common cause of ambiguous genitalia in a female child

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Flashcards: Disorders of Sexual Development

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Syndromes associated with SCFE include: _____ syndrome, Klinefelter's syndrome

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Syndromes associated with SCFE include: _____ syndrome, Klinefelter's syndrome

Turner's

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