[Drug fever due to isoniazid]

Drug fever is an uncommon manifestation of isoniazid intolerance. A patient with tuberculous peritonitis is presented with a diagnostic problem, because of continuous and spiking fever, while she was on isoniazid. The fever disappeared after discontinuation of the drug. For confirmation of the drug fever, isoniazid was given on two occasions. Fever respond was demonstrated on rechallenge. This case calls attention to uncommon adverse reaction of isoniazid in patients who are treated with isoniazid.