A 24-year-old man is evaluated for mild hypercalcaemia found incidentally (calcium 10.7 mg/dL, PTH 55 pg/mL). He is asymptomatic, renal function and DEXA are normal, and he reports his father had lifelong 'mild high calcium' never operated upon. Fractional excretion of calcium is very low, with a calcium to creatinine clearance ratio of 0.008. The most appropriate management is:
- A Focused parathyroid exploration after sestamibi localisation
- B Four-gland exploration with subtotal parathyroidectomy
- C Reassurance and no surgery, with genetic testing for CASR mutation ✓
- D Cinacalcet therapy titrated to normocalcaemia
Correct answer: C. Reassurance and no surgery, with genetic testing for CASR mutation
Explanation
Familial hypocalciuric hypercalcaemia mimics mild primary hyperparathyroidism, but the calcium to creatinine clearance ratio below 0.01, family history of untreated hypercalcaemia, and young age point to FHH, caused by inactivating CASR mutations resetting the calcium-PTH curve. Parathyroidectomy in FHH does not cure the condition and is the classic wrong operation. Indian exam convention emphasises this ratio as the discriminating test. Observation alone is appropriate since FHH is benign.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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