Etiology and mechanisms of drug-induced lupus.

Systemic rheumatic symptoms occur with widely different frequencies as a side effect of long-term therapy with some 39 medications currently in use. Because symptoms are nonspecific, subjective, and protean, diagnosis of drug-induced lupus (DIL) requires awareness of this risk of chronic medication. However, laboratory features and the characteristic of full recovery after discontinuing treatment are helpful in differentiating drug-induced from spontaneous lupus or other syndromes. Drug-induced lupus is probably mediated by reactive drug metabolites, not the ingested medications, and susceptibility to neutrophil-mediated oxidative transformation is a property of ten lupus-inducing drugs reported so far. Mechanisms for DIL modeled after drug hypersensitivity reactions are unsupported experimentally and inconsistent with the features of DIL. However, several new lines of investigation using mouse models have opened up promising leads into the origin of autoreactive T cells and disease development in DIL.