Pellagra encephalopathy among tuberculous patients: its relation to isoniazid therapy.

Eight cases of pellagra, diagnosed on the grounds of neuropathological findings and retrospective study of clinical data, were found among 106 necropsy cases of tuberculosis. Although these eight patients had shown various mental, neurological and gastrointestinal symptoms, as well as skin lesions, the diagnosis of pellagra had not been made clinically. In all the patients, pellagra symptoms appeared during isoniazid therapy. Death occurred 4 to 16 weeks later. Isoniazid inhibits the conversion of tryptophan to niacin and may induce pellagra, particularly in poorly nourished patients. Pellagra should be suspected whenever tuberculous patients under treatment with isoniazid develop mental, neurological or gastrointestinal symptoms, even in the absence of typical pellagra dermatitis.