Makindo Medical Notes

Related Subjects: |Systemic Lupus Erythematosus (SLE) |Drug induced Lupus Erythematosus |Discoid lupus erythematosus (DLE) |Neonatal Lupus Erythematosus |Raynaud's Phenomenon |Polymyositis |Dermatomyositis |Polyarteritis nodosa |Rheumatoid Arthritis |Systemic Sclerosis (Scleroderma) |Rheumatology Autoantibodies |Overlap Syndrome |Inclusion Body Myositis |Inflammatory Myopathies |Psoriatic Arthritis |Adult Onset Still's Disease |Alkaptonuria |Behcet's Syndrome

💊 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).

🔬 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

📚 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.