Serum neopterin as a marker for reactional states in leprosy.

Reactions, a relatively common phenomenon among leprosy patients in treatment, require early detection and proper management to prevent serious sequelae. It is generally accepted that reactional states are immunologically mediated and, as such, usually improve with immunomodulatory treatments such as corticosteroids or thalidomide. Neopterin, a product of gamma-interferon-activated macrophages, is a marker for cell-mediated immune activation and may be useful to detect reactional states in leprosy. Here, we compared neopterin levels in single serum samples from leprosy patients with and without reaction with untreated controls and, when available, serial samples among patients with and without reaction. Levels in the single sample measurements, conducted in 22 patients with a reversal reaction (mean 14.5 nmol l(-1), S.D. 8.7) and 13 with erythema nodosum leprosum (mean 16.9 nmol l(-1), S.D. 13.6), were significantly higher (P=0.02 and P=0.001, respectively) than levels in 26 untreated patients (mean 9.1 nmol l(-1), S.D. 7.3). Values above the upper limit of normal (10 nmol l(-1)) were found in seven of 26 untreated patients, 14 of the 22 reversal reaction patients (P=0.01) and 10 of the 13 ENL patients (P=0.003). Serial serum samples, obtained from six patients that developed reactions and 14 that remained free of reaction, indicated that reversal reaction or erythema nodosum leprosum paralleled a concomitant increase in the serum neopterin level. Neopterin levels generally declined upon corticosteroid therapy. Neopterin may be a useful marker for reactional states in leprosy by providing a laboratory parameter to assess the onset, progression, response to therapy and resolution.