Turner syndrome and DSD — structured oral station (12 minutes)

Opening prompt — "What is your working diagnosis and what is the single mechanism?"

Model response — the diagnosis and mechanism: ^[1]

• "Her phenotype is classical Turner syndrome: short stature, primary amenorrhoea, shield chest, cubitus valgus and a webbed neck. The short stature is driven by SHOX haploinsufficiency — the SHOX gene on the pseudoautosomal region of the X chromosome is essential for linear bone growth."
• "I would confirm the diagnosis with a full karyotype of at least 30 cells, with a screen for Y-chromosome material — a 20-cell karyotype or FISH would miss low-level mosaicism and structural variants, and the Y-chromosome question changes the gonadoblastoma management."^[1]

Probe 1 — "What baseline surveillance would you arrange?"

• "Cardiac is the priority: echocardiogram AND cardiac MRI at diagnosis. Echo alone misses the aortic arch and descending aorta — and the aorta is the organ that kills via dissection in Turner syndrome. I would add interval aortic imaging and lifelong blood-pressure surveillance."^[1][2]
• "Renal ultrasound for horseshoe kidney and collecting-system anomalies; thyroid function and antibodies, fasting glucose/HbA1c and lipids; baseline audiology and bone age; and an FSH/LH/oestradiol/AMH to document the gonadal dysgenesis."^[1]

Probe 2 — "She is 14 and asking about puberty. Walk me through the hormone plan."

• "The cardinal principle is sequencing: growth hormone first, oestrogen second. GH was started in childhood to improve final adult height. Oestrogen induction is begun around age 11 to 12 at low dose and ramped gradually over 2 to 3 years to mimic a normal pubertal curve. Premature oestrogen fuses the epiphyses and steals final height."^[1]
• "A progestogen is added once breakthrough bleeding occurs or after 1 to 2 years of unopposed oestrogen, for endometrial protection. Combined HRT continues until the usual age of menopause to protect bone and cardiovascular health."^[1]

Probe 3 — "She eventually asks whether she will be able to have children. What do you say?"

• "I address her fertility intentions honestly and early. Autologous oocyte retrieval is rarely possible because the streak gonads have already caused premature ovarian insufficiency by the time most women with Turner syndrome present. Oocyte or embryo donation is the commonest route."^[1]
• "But before any pregnancy I insist on cardiac clearance with cardiac MRI of the ascending aorta — if it is dilated per the Gravholt 2024 thresholds, pregnancy is contraindicated because of aortic dissection risk. Even a cleared pregnancy is high-risk obstetric care."^[3]

Probe 4 — "She is frightened this means she is 'abnormal'. What do you say?"

This is a scored communication domain — demonstrate it out loud: ^[1]

• Move to her eye level, use her name, acknowledge the fear and the language: "Turner syndrome is a chromosomal difference, not a defect. You will grow, you will go through puberty with our help, your bones and heart will be looked after, and we will plan your fertility options with you when you are ready. There is a whole team behind you, and you will not be sent away to cope alone."^[1]

Probe 5 — Vignette: "A newborn on the postnatal ward has ambiguous genitalia. What is your immediate plan?"

• "The immediate lethal exclusion is salt-wasting congenital adrenal hyperplasia. I check urgent electrolytes, glucose and 17-hydroxyprogesterate within hours, and treat empirically with IV fluids and hydrocortisone if the electrolytes fit — I do not wait for the result."^[4]
• "I karyotype the infant (30 cells), arrange pelvic ultrasound for uterus and gonads, and convene the multidisciplinary team — paediatric endocrinology, urology, genetics, psychology. Critically, I do NOT assign sex before the workup and the family are seen by the team; I give them a single named clinical contact."^[5]