Isoniazid-induced fever.

A rare case of isoniazid (INH)-induced fever is described. A 27-year-old woman diagnosed with miliary tuberculosis (TB) began to receive combined anti-TB treatment including INH, ethambutol, rifampicin and pyrazinamide on the second day of hospitalization. A spiked fever developed in the afternoon of the seventh hospital day. There was no evidence of a hypersensitivity reaction. All examinations including liver function tests, routine biochemistry tests, serum titer of antinuclear antibody and rheumatoid factor were within normal limits. The blood leukocyte count was also within normal range and no evidence of infection at other sites was found. Following the discontinuance of anti-TB agents, the patient's body temperature gradually returned to normal. When the patient was rechallenged with INH, the high fever recurred. The fever subsided again after the discontinuance of INH, and her recovery followed a smooth course thereafter, on combination therapy with rifampicin, ethambutol and pyrazinamide. This experience demonstrates the potential of INH to cause an isolated fever without other manifestations, which may be misdiagnosed as an infectious process. Though it is very rare, INH-induced fever must be considered when fever develops during anti-TB treatment.