💊 Drug-induced lupus erythematosus (DILE) is an autoimmune condition caused by a reaction to certain medications. ⚠️ It tends to be more benign than idiopathic SLE, with rare renal, skin, or neurological involvement.

🧬 About

Resembles systemic lupus erythematosus but usually milder.
Key distinction: renal, neurological, and cutaneous involvement is uncommon.
Improves after withdrawal of the offending drug.

⚖️ Risk Factors

Older age group compared with classic lupus.
Pharmacogenetics: slow acetylator status.
Genetic predisposition: HLA DR4, DR2, DR3, DR0301, DQB1, B8, C4 null allele.

💊 Common Culprit Drugs

High yield: Isoniazid, Procainamide, Hydralazine, Penicillamine, Phenytoin.
Biologics: TNF-α inhibitors (etanercept, infliximab, adalimumab).
Other causes: Minocycline, Quinidine, Methyldopa, Chlorpromazine, Sulfasalazine, Capoten (captopril).
Levamisole-adulterated cocaine – increasingly recognised cause.

🩺 Clinical Features

Onset: usually after 3–6 months of therapy (sometimes up to 10 years).
Systemic: fever, malaise, weight loss.
MSK: polyarthritis or migratory arthralgia (often symmetrical).
Serositis: pleuritis or pericarditis.
Skin: annular or papulosquamous lesions on sun-exposed areas (less severe than idiopathic SLE).

Drug-induced lupus rash

🔬 Investigations

FBC & U&E: usually normal.
Complement (C3/C4): usually normal (contrast with SLE where low).
ANA: positive in ~90% (homogeneous pattern).
Anti-dsDNA: typically negative.
Anti-histone antibodies: positive in >95% of DILE cases – hallmark test.
ESR: may be raised.

🛠️ Management

🚫 Stop the causative drug – symptoms usually resolve within weeks to months.
NSAIDs or low-dose steroids for symptomatic relief in persistent arthritis/serositis.

📊 Exam Tip – DILE vs SLE

Feature	Drug-Induced Lupus	Systemic Lupus (SLE)
Age	Older	Younger (esp. women of childbearing age)
Time course	Months–years after exposure	Chronic/relapsing
Renal/CNS involvement	Rare	Common
ANA	Positive, homogeneous	Positive, mixed patterns
Anti-dsDNA	Negative	Positive (specific)
Anti-histone	Positive in >95%	Positive in 50–70%
Management	Stop drug → resolution	Immunosuppression needed

📚 References

DermNet NZ – Drug-induced lupus erythematosus

Cases — Drug-Induced Lupus Erythematosus (DILE)

Case 1 — Hydralazine-related 💊: A 54-year-old man on long-term hydralazine for resistant hypertension develops fatigue, arthralgia, low-grade fever, and a photosensitive rash. Bloods: ANA positive, anti-histone antibody positive, normal complement levels. Diagnosis: drug-induced lupus from hydralazine. Symptoms improve on drug withdrawal.
Case 2 — Procainamide-associated ❤️: A 61-year-old woman treated with procainamide for atrial fibrillation presents with pleuritic chest pain and arthralgia. Exam: small pleural effusion. Autoantibodies: anti-histone strongly positive, dsDNA negative. Diagnosis: drug-induced lupus from procainamide. Managed with discontinuation and NSAIDs.
Case 3 — Anti-TNF induced 🌐: A 45-year-old man with rheumatoid arthritis on infliximab reports photosensitive rash, oral ulcers, and joint pains. ANA and anti-dsDNA are positive, but disease resolves after stopping the drug. Diagnosis: anti-TNF–induced lupus-like syndrome. Managed with drug cessation and short steroid course.

Teaching Point 🩺: DILE resembles SLE but usually spares the kidneys and CNS. Hallmarks are exposure to culprit drugs (hydralazine, procainamide, isoniazid, minocycline, anti-TNF agents), positive ANA/anti-histone antibodies, and resolution after withdrawal.

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Drug induced Lupus Erythematosus