Intradermal tophi in gout: a case-control study

OBJECTIVE: To describe the characteristics of intradermal tophi in patients with gout and search for factors associated with their development. METHODS: This is a case-control study of patients with gout: cases (Group A, n = 21) had intradermal (not subcutaneous) plaques of monosodium urate (MSU) crystals located in sites distant to articular or paraarticular structures, and controls (Group B, n = 42) had gout but no intradermal tophi. Both Group A and Group B were paired by sex, age (+/-5 years), and duration of the disease (+/-3 years). Analysis included serum and urinary uric acid levels at first visit, radiographic stage of gout, the presence of associated diseases, and previous therapy, specifically, chronic glucocorticoid and diuretic usage. RESULTS: Intradermal tophi were located in the legs, forearms, buttocks, thighs, arms, and abdominal wall. Patients in Group A had a greater number of nonintradermal tophi in common sites (11.9+/-12.5 vs. 4.2+/-7.9, mean +/- SD; p = 0.018), decreased glomerular filtration rate (46.74+/-25.11 vs. 70.87+/-30.18 ml/min; p = 0.042), advanced radiographic changes (57.2 vs. 7.1%; p = 0.0001), and longterm glucocorticoid self-medication (76 vs. 36%; p = 0.006). We found no differences in other associated diseases between groups. CONCLUSION: Intradermal tophi were commonly found in the legs and forearms, and less frequently in the buttocks, thighs, and abdominal wall of gouty patients, and were associated with longterm self-prescribed glucocorticoids and chronic renal failure. The occurrence of intradermal tophi in these patients appeared to correlate with advanced disease.