A 72-year-old with sudden calf pain after starting a new drug
A 72-year-old man with hypertension, type 2 diabetes and chronic kidney disease (eGFR 38 mL/min/1.73 m²) presents with 3 days of severe left calf pain and swelling. He started a new medication 6 weeks ago for gout prophylaxis. He is afebrile. The calf is warm, tender and 3 cm larger than the right. He has no history of venous thromboembolism or recent immobilisation, and he walks daily. Doppler ultrasound shows no deep vein thrombosis. Laboratory tests: CRP 18 mg/L, creatine kinase normal, urate 0.41 mmol/L (6.9 mg/dL), white cell count 8.2 × 10⁹/L. He is on ramipril, metformin, atorvastatin and the new drug.
1. What is the likely diagnosis and which medication is the probable culprit? Explain the mechanism.
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The picture is of an acute inflammatory myopathy or myositis-like syndrome, not cellulitis or DVT (ultrasound negative, no fever, normal CK is possible early or with focal disease but should be repeated).
The key clue is the timing: symptoms began 6 weeks after starting a drug for gout prophylaxis in a patient with chronic kidney disease. The probable culprit is colchicine, which is commonly used for gout prophylaxis and is a well-recognised cause of a myopathy and neuromyopathy, particularly in renal impairment. Colchicine is cleared renally and hepatically; CKD, interacting drugs (clarithromycin, ciclosporin, statins, fibrates) and advanced age all raise toxicity risk. The mechanism is microtubule disruption leading to a vacuolar myopathy, often with proximal weakness and sometimes neuropathy; CK may be normal or only mildly raised.
Other drug causes to consider: statin-induced myopathy (he takes atorvastatin; risk increased by CKD, diabetes, and interacting drugs), and fibrates. Statin myopathy usually causes CK elevation but can be normal.
The absence of fever and normal white cell count argue against cellulitis; the normal ultrasound argues against DVT. The diagnosis is clinical and supported by drug withdrawal and, if needed, EMG or muscle biopsy.
2. How would you manage this patient, including immediate steps and safe alternatives for gout prophylaxis?
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Immediate steps:
- Stop the suspected drug (colchicine) and review the statin - hold it temporarily until the picture clarifies.
- Repeat CK, renal function, and consider EMG/nerve conduction studies and, if the diagnosis remains unclear, MRI of the calf and muscle biopsy.
- Supportive care: analgesia, physiotherapy, monitor renal function (rhabdomyolysis risk if CK rises), and watch for respiratory compromise if weakness is generalised.
- Review interacting medications (macrolides, ciclosporin, verapamil, fibrates) and avoid them.
Gout prophylaxis alternatives in CKD:
- Low-dose colchicine is contraindicated or must be dose-reduced in significant CKD; avoid entirely here after this reaction.
- NSAIDs are relatively contraindicated with eGFR 38.
- Low-dose prednisolone (e.g. 5 mg daily) can be used for short-term prophylaxis but has metabolic costs in diabetes.
- IL-1 blockade (anakinra or canakinumab) is an option for refractory cases but is expensive and infection risk must be weighed.
- Urate-lowering therapy should be optimised: allopurinol is preferred, started low (e.g. 50-100 mg) and titrated to a target urate <0.36 mmol/L (6 mg/dL), with dose adjustment for renal function; febuxostat is an alternative but caution in cardiovascular disease.
Document the adverse reaction, counsel the patient, and arrange follow-up to confirm resolution after withdrawal.