Cushing syndrome in children — branching viva

Station opening

Examiner: "Tell me the single bedside observation that frames every overweight child you suspect of Cushing syndrome, and why it matters." [1]

Strong candidate (must-hit)

• The observation is the growth chart. In a child, weight gain with a falling height velocity is Cushing until proven otherwise, because cortisol suppresses the growth-hormone axis. In simple exogenous obesity the child keeps growing, often with an advanced bone age, because over-nutrition drives growth. It matters because the growth chart separates the disease from its commonest mimic before any blood test, and missing it means treating genuine Cushing as simple obesity. [1]

Weak candidate

• "Cushing causes central obesity and a moon face." [1]

Branch A — The adolescent who stopped growing

Examiner: "A 13-year-old girl has gained weight, developed purple striae and her height has crossed from the 50th to the 10th centile. Name the three first-line confirmatory tests and the principle that you use at least two." [3]

Strong

• The three first-line tests are a late-night (midnight) salivary or serum cortisol — the most sensitive single test because loss of the diurnal rhythm is the earliest change — a 24-hour urinary free cortisol, and an overnight dexamethasone suppression test with dexamethasone 15 µg per kilogram capped at 1 mg, where an 8 am cortisol not suppressed below 1.8 µg per decilitre supports Cushing. Two are used because no single test is perfect and the disease is cyclic. [3]

Weak

• "I would check a random cortisol." [3]

Branch B — The localisation fork

Examiner: "Cortisol excess is confirmed. What single result splits the investigation, and where does each arm send you?" [5]

Strong

• Plasma ACTH is the fork. A high or inappropriately normal ACTH means ACTH-dependent disease — pituitary or, rarely, ectopic — and sends you to a dynamic gadolinium pituitary MRI, with bilateral inferior petrosal sinus sampling when the MRI is negative or non-lateralising. A suppressed low ACTH means ACTH-independent disease and sends you to adrenal CT or MRI. A central-to-peripheral ACTH ratio above two at baseline, or above three after corticotrophin-releasing hormone, confirms pituitary disease. [5]

Weak

• "I would order an MRI of everything." [5]

Branch C — The young child with an adrenal mass

Examiner: "A four-year-old boy has a five-centimetre adrenal mass, virilisation and a high DHEAS. What is the likely diagnosis, what syndrome should you consider, and why does his age matter?" [5]

Strong

• The likely diagnosis is adrenocortical carcinoma: a large lesion over four centimetres, androgen excess with virilisation, and a high DHEAS point to carcinoma rather than a benign adenoma. Consider Li-Fraumeni syndrome (TP53), which is strongly associated with childhood adrenocortical carcinoma. His age matters because adrenal and genetic causes predominate in children under seven, whereas pituitary Cushing disease dominates over seven and in adolescents. Management is complete surgical resection with adjuvant therapy guided by stage. [5] [9]

Weak

• "It is probably a benign adrenal adenoma — I would remove it." [5]

Branch D — The child on inhaled steroids

Examiner: "A child on high-dose inhaled fluticasone has a moon face and a suppressed ACTH. What is the diagnosis, and what is the cardinal rule about his steroids?" [4]

Strong

• This is iatrogenic (exogenous) Cushing syndrome from systemic absorption of inhaled steroid — the single most common cause of a Cushingoid child. The exogenous steroid suppresses the axis, so ACTH and endogenous cortisol are both low. The cardinal rule is never to stop the steroids abruptly, because the suppressed axis cannot generate cortisol and the child will develop adrenal crisis; taper slowly with the prescribing team and provide intercurrent-illness cover. [4]

Weak

• "Stop the inhaled steroid immediately." [4]

Branch E — The cured child on the ward

Examiner: "A child is in recovery the day after successful transsphenoidal surgery for Cushing disease. Her morning cortisol is low and she is hypotensive. What is happening and what do you do?" [6]

Strong

• She is adrenally insufficient because the cure has removed the cortisol excess and her suppressed normal pituitary tissue cannot yet generate ACTH. A low morning cortisol after surgery is the sign of cure, not of failure. Treat as adrenal crisis: give stress-dose hydrocortisone intravenously, with fluids and glucose as needed, do not wait for confirmatory tests, then continue glucocorticoid replacement until the axis recovers over six to eighteen months, with a parent-held emergency injection and a MedicAlert. [6]

Weak

• "The operation has failed — call the surgeon to re-explore." [6]

Close

Examiner: "Summarise your approach to Cushing syndrome in a child in one sentence." [1]

Strong

• "I let the growth chart guide me — weight rising with height falling is Cushing until proven otherwise — confirm with two of three tests, split ACTH-dependent from ACTH-independent by the ACTH level, treat the source surgically, and remember that every cured child is adrenally insufficient and needs stress-dose glucocorticoid." [1] [4]