Disorders of Sex Development (DSD) & Ambiguous Genitalia - High-Yield Viva Questions
| Question | Answer / Practical Pearls |
|---|---|
| What is the fundamental bedside clinical rule when evaluating a newborn with ambiguous genitalia? | • THE CARDINAL AXIS: Are gonads palpable or non-palpable? 1. Bilateral Non-Palpable Gonads: Presume ovaries until proven otherwise $\to$ 46,XX DSD $\to$ The most common, critical, and life-threatening cause is Congenital Adrenal Hyperplasia (21-Hydroxylase Deficiency) until proven otherwise! 2. Bilateral Palpable Gonads: Presume testes $\to$ 46,XY DSD (Androgen Insensitivity Syndrome, $5\alpha$-reductase deficiency, or testosterone biosynthetic defects) or rarely Ovotesticular DSD. 3. Unilateral Palpable Gonad: Asymmetric DSD $\to$ Mixed Gonadal Dysgenesis (45,X/46,XY) or Ovotesticular DSD. |
| Describe the Prader Staging system for virilization of female external genitalia. | • Stage 1: Clitoromegaly only, normal separate urethral and vaginal orifices. • Stage 2: Marked clitoromegaly with posterior labial fusion, creating a funnel-shaped vestibule. • Stage 3: Greater clitoromegaly (phallic structure) with a single urogenital sinus orifice at the base of the phallus; extensive posterior labioscrotal fusion. • Stage 4: Phallic urethra with complete labioscrotal fusion resembling an empty scrotum; meatus at perineum or base. • Stage 5: Normal phenotypic male external genitalia with penile urethra, but empty scrotum (bilateral non-palpable testes). |
| Why does a salt-wasting CAH infant typically decompensate between Day 5 and Day 14 of life? | • At birth, maternal aldosterone and cortisol cleared from maternal circulation provide temporary protection. • By Day 5 to 7, maternal steroid hormones are completely degraded, exposing the infant's endogenous complete mineralocorticoid and glucocorticoid deficiency. • Without aldosterone, the renal distal tubules cannot reabsorb sodium or secrete potassium and hydrogen ions, resulting in progressive severe salt wasting, hypovolemic shock, hyponatremia, hyperkalemia, and metabolic acidosis. |
| Give the emergency resuscitation protocol for acute neonatal adrenal crisis. | 1. Airway & Oxygen: $100\%\text{ O}_2$, maintain patent airway. 2. Fluid Resuscitation: Two wide-bore IV lines; infuse Normal Saline (0.9% NaCl) at $20\text{ mL/kg}$ over 20-30 minutes. Repeat if perfusion remains poor. NEVER use potassium-containing fluids! 3. Hypoglycemia: $2\text{ mL/kg}$ of 10% Dextrose (D10W) slow IV push. 4. Myocardial Membrane Stabilization: If peaked T waves or widened QRS on ECG, give 10% Calcium Gluconate $0.5-1.0\text{ mL/kg IV}$ over 5-10 minutes. 5. Glucocorticoid: Inj. Hydrocortisone sodium succinate $25\text{ mg IV bolus}$ (or $50-100\text{ mg/m}^2$), followed by $25-50\text{ mg/m}^2/\text{day}$ divided Q6H. 6. Maintenance Mineralocorticoid: Oral Fludrocortisone ($0.1-0.2\text{ mg/d}$) + oral NaCl ($1-2\text{ g/d}$) added once oral feeds resume. |
| What is the modern consensus (Chicago Consensus) regarding gender assignment and surgical timing in DSD? | • Communication: Avoid premature declaration of sex. Use neutral terms ('baby with incompletely developed genitals'). • Multidisciplinary Team: Pediatric endocrinologist, geneticist, pediatric urologist/surgeon, and child psychologist. • 46,XX CAH: Gender assignment is Female, because the internal reproductive anatomy (uterus, fallopian tubes, ovaries) is completely normal, with full future reproductive potential. • Surgical Timing: Cosmetic surgeries are not medical emergencies. Neurovascular-sparing clitoroplasty and pull-through vaginoplasty are deferred to 6-12 months of age or older, allowing parental participation and informed surgical planning. |