Skin anergy and tuberculosis.

In our experience tuberculin skin anergy (negative response to 10 TU Mantoux) occurs in 8% of patients with tuberculosis. In this study we compare 81 patients with skin anergy and proven tuberculosis with a background reactive population of patients with tuberculosis. Patients with skin anergy and tuberculosis were older and had fewer symptoms--less cough, less sputum production, less haemoptysis, less malaise, less chest pain--than patients with skin reactivity. There was no difference with respect to male/female ratio, marital status, smoking habits, coexistent major illness, prescribed medications at diagnosis, nor the proportion of patients with extrapulmonary tuberculosis, previous history of BCG vaccination or past history of tuberculosis. Comparison of chest radiographs showed more advanced, more bilateral and more miliary disease in the anergic patients. Pyrexia and elevated ESR at diagnosis were also more common in this group. Fewer of the anergic group of patients were consistently culture negative after 1 month's treatment compared to the background population. Mortality was higher in the anergic group, but this excess mortality occurred from causes other than tuberculosis. Repeat Mantoux testing was performed in 20 of the 81 anergic patients, after a minimum of 3 months of antituberculous chemotherapy, and 14 had become tuberculin positive, suggesting that tuberculin skin anergy may be a temporary phenomenon.