[Lupus syndrome during treatment with isoniazid].

In a young girl, aged 17 years, there occurred, 9 months after starting treatment with isoniazid and rifampicin, clinical signs of rheumatoid arthritis with facial erythema of vespertilio type. The presence of L.E. cells and antinuclear antibodies with a high titer, the rapid disappearance of all the clinical signs on stopping isoniazid, and the transient exacerbation of the syndrome on giving a single dose of isoniazid, gave the diagnosis of systemic lupus erythematosus induced by isoniazid. 18 months after stopping the drug, the patient is apparently cured, but there persists in the serum antinuclear antibodies in low concentration (1/200). A study of acetylation of isoniazid in this patient and her 3 sisters, showed that they were all of the slow acetylating phenotype. The late prognosis of this disease and the physiopathological value of the slow acetyl phenotype are worth discussion.