NEW ORLEANS — Abnormal antinuclear antibody, antistreptolysin O titer, and rapid plasma reagin tests were all negative. A chest x-ray showed mild cardiomegaly, but was otherwise unremarkable. A purified protein derivative (PPD) was reactive at 48 hours. Histology showed a lobular infiltrate and vasculitis, with a substantial amount of extravasated red blood cells.
The diagnosis was erythema induratum. The earlier negative PPD test could have been incorrectly read, or she could have been exposed and seroconverted after the initial test. The patient received combination therapy with isoniazid, rifampin, and pyrazinamide for 9 months. Within 3 months, she had considerable reduction in induration, erythema, and discomfort. By the end of treatment, all symptoms had resolved.
However, 3 years later, she presented with a new painful, erythematous plaque on her left ankle. She denied any systemic complaints including fever, chills, cough, or weight loss. Histology was consistent with nodular vasculitis and similar to the first lesion. She was successfully treated with prednisone at a starting dose of 60 mg, tapered over 12 days.
The nodular vasculitis diagnosis was something of a surprise because erythema induratum was expected, said Jennifer Dempsey, M.D., of Vanderbilt University, Nashville, Tenn., at the annual meeting of the American Academy of Dermatology. “We know that inadequately treated cases of erythema induratum may recur,” she said.
The recurrence could have been related to the TB therapy, she noted.
Nodular vasculitis and erythema induratum were initially considered one entity, Dr. Dempsey said. More recently, the disorders have been divided based on their association with TB: Nodular vasculitis is not associated with the infection, while 30%–80% of erythema induratum is associated.
A healthy 63-year-old Vietnamese woman presented with a painful, swollen left ankle for 3 months but had no trauma to the area. She had a 5-by-10-cm erythematous, warm, indurated, mildly tender plaque. She also had a mild, nonproductive cough of 3 years' duration; a previous PPD was negative. She had been treated with oral antibiotics and systemic potassium iodide without improvement. What's your diagnosis?
Photos courtesy Dr. Jennifer Dempsey