A patient with multiple systemic problems presents with a white, frost-like deposit on the oral mucosa, arms and trunk. What is the most likely underlying condition?

Correct answer: D. End-stage renal disease (uremic frost)

• A. Addison disease causes generalised HYPERpigmentation — diffuse brown mucosal and skin patches from excess ACTH/MSH — the visual opposite of a white frost.
• B. Hypoparathyroidism causes hypocalcaemia with tetany, paraesthesia and enamel hypoplasia if it occurs during development — not a cutaneous frost.
• C. Cushing syndrome produces moon facies, buffalo hump, striae and thin skin, not crystalline surface deposits.
• D. CORRECT. UREMIC FROST is the deposition of crystallised urea on the skin and mucosa when the blood urea nitrogen is extremely high, as in END-STAGE RENAL DISEASE. It appears as a fine white powdery coating. Other oral findings in ESRD include an ammoniacal odour, xerostomia, mucosal pallor from anaemia, uremic stomatitis, and a ground-glass loss of lamina dura from renal osteodystrophy.

Note: Practical points for ESRD: treat on the day AFTER dialysis, avoid the arm with the AV fistula for blood pressure, and adjust renally cleared drugs.