EpistemisSkin deposit of tophi
Specialty: Endocrine and metabolic.
Why it occurs
- Uncontrolled chronic hyperuricemia (sustained plasma uric acid concentrations above the physiological saturation point of 6.8 mg/dL, which causes the precipitation and nucleation of monosodium urate crystals in the subcutaneous tissue, joints and tendons)
- Advanced chronic renal failure (drastic decrease in fractional excretion and renal clearance of uric acid)
- Chronic tumor lysis syndrome or extensive psoriasis (massive cellular turnover with endogenous overproduction of purines and uric acid)
- Prolonged use of loop or thiazide diuretics without adjuvant hypouricemic therapy (volume depletion with increased proximal tubular reabsorption of urate)
Initial workup
Determination of uric acid in serum; plasma creatinine and urea nitrogen; 24-hour urinary uric acid clearance; high-resolution articular ultrasound (demonstration of the double contour sign in the articular cartilage and visualization of echogenic tophi); plain x-ray of the affected joints (demonstration of punched-out bone erosions with hanging edges characteristic of tophaceous gout); and arthrocentesis with aspiration of fluid or tophus material for confirmation by polarized light microscopy (demonstration of needle-shaped monosodium urate crystals with strong negative birefringence).
red flags
Tophi that spontaneously erode the overlying skin, secreting a pasty, chalky whitish material, associated with severe acute inflammatory signs of local bacterial superinfection (cellulitis or concomitant septic arthritis), or large tophi located in the cervical spine that cause symptoms of acute spinal cord compression (paresthesias, paraparesis or sphincter dysfunction).
Standard management
- Allopurinol — xanthine oxidase enzyme inhibitor, drug of choice to reduce the synthesis of uric acid, initiated at a dose of 100 mg/day and progressively titrated until reaching target uric acid levels of less than 5.0 mg/dL to promote the dissolution of tophi
- Febuxostat — selective non-purine xanthine oxidase inhibitor, useful in patients with intolerance or hypersensitivity to allopurinol
- Pegloticasa — recombinant pegylated intravenous urate oxidase enzyme, indicated exclusively for cases of severe refractory and debilitating tophaceous gout due to its high capacity to quickly dissolve tophi
- Colchicine — administered at low doses of 0.5 mg once or twice a day as mandatory anti-inflammatory prophylaxis during the first 3 to 6 months after the start of uricemia-lowering therapy to avoid acute gout attacks due to crystal mobilization
Educational guidance for study. It is NOT a prescription recommendation. The actual choice depends on the cause, the patient, and current guidelines.
- Area
- Endocrine and metabolic
- Listed causes
- 4
- Treatment options
- 4