Intradermal tophi in gout: a case-control study.

Abstract

To describe the characteristics of intradermal tophi in patients with gout and search for factors associated with their development. 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. 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. 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.