Calcinosis cutis of the thumb

A 57‐year‐old woman receiving intermittent haemodialysis presented with a six‐week history of atraumatic, painful, firm swelling of her right thumb. At presentation she was taking calcitriol 0.25μg daily and lanthanum carbonate 1000mg three times per day with meals. Examination revealed punctate erosions, firm papules, and overlying erythema (Figure, A). Thumb circumference at the interphalangeal crease was 13.5cm compared with 5.5cm on the left. Serum phosphate was 2.88mmol/L (reference interval [RI], 0.75–1.50mmol/L), corrected calcium 2.36mmol/L (RI, 2.10–2.60mmol/L) and parathyroid hormone 27.6pmol/L (RI, 1.6–6.9pmol/L). X‐ray identified soft tissue calcification at the volar aspect of the right thumb confirming a diagnosis of calcinosis cutis (Figure, B). Intravenous sodium thiosulfate 25g was started three times per week. At two months, thumb circumference decreased to 11.2cm, and repeat x‐ray showed reduced calcification (Figure, C). Therapy is planned to continue for a total of 12 months. Alternative treatments include topical or intralesional injection of sodium thiosulfate.1