Drug-induced lupus

In drug-induced lupus not all the typical features of systemic lupus erythematosus are seen, with renal and nervous system involvement being unusual. It typically resolves after the trigger drug is stopped; the latent period can be long (≈1 month to >10 years), making causality easy to miss. Drug-induced SCLE can be clinically/serologically indistinguishable from idiopathic SCLE

Features

• arthralgia
• myalgia
• skin (e.g. malar rash) and pulmonary involvement (e.g. pleurisy) are common
• ANA positive in 100%, dsDNA negative
• anti-histone antibodies are found in 80-90%
• anti-Ro, anti-Smith positive in around 5%

• Systemic DIL (classic “drug-induced SLE”)—examples of definite associations: chlorpromazine, methyldopa, hydralazine, isoniazid, D‑penicillamine, minocycline.
• Drug-induced SCLE—UK MHRA signal: Proton pump inhibitors (omeprazole, esomeprazole, lansoprazole, pantoprazole, rabeprazole) are linked to very infrequent SCLE, often in sun-exposed areas and may be accompanied by arthralgia; risk may recur with a different PPI (class effect).

Most common causes

• procainamide
• hydralazine

Less common causes

• isoniazid
• minocycline
• phenytoin