Successful desensitization therapy for a patient with isoniazid-induced hypersensitivity pneumonia

A 57-year-old male was diagnosed with mycobacterium tuberculoma and was treated with isoniazid, rifampicin, ethambutol, and pyrazinamide. Three weeks after initiation of treatment, he presented with fever and appetite loss. Chest radiograph showed diffuse micronodular shadows on both lung fields. High-resolution chest computed tomography findings were diffuse parenchymal micronodules in both lungs, which was consistent with hypersensitivity pneumonia. Because drug-induced pneumonia was suspected, the antituberculous regimen was discontinued. The symptoms and diffuse micronodular shadows improved. A drug lymphocyte stimulation test was only positive for isoniazid, so we suspected that the pneumonia was induced by isoniazid. Rifampicin and ethambutol were reintroduced without any recurrence of the abnormal shadows. Next, we tried desensitization to isoniazid over a period of two weeks, which was successful without any adverse events. Although isoniazid-induced pneumonia is extremely rare, it is important to recognize that isoniazid can cause such an adverse reaction. In addition, drug desensitization may be useful in drug-induced pneumonia.