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Monday, August 11, 2025

Lupus (Systemic Lupus Erythematosus – SLE)


Definition
Lupus, most commonly referring to systemic lupus erythematosus (SLE), is a chronic autoimmune disease characterized by the production of autoantibodies against nuclear and cytoplasmic antigens. This leads to immune complex formation, complement activation, and inflammation affecting multiple organ systems including the skin, joints, kidneys, heart, lungs, and central nervous system.

Epidemiology

  • Global prevalence: approximately 20–150 cases per 100,000 people.

  • Predominantly affects women of childbearing age (female-to-male ratio ~9:1).

  • Higher prevalence in African, Asian, Hispanic, and Native American populations.

  • Onset most common between ages 15 and 45.

Etiology and Risk Factors

Genetic Factors

  • Associations with HLA-DR2, HLA-DR3, and other immune regulatory gene variants.

Environmental Triggers

  • Ultraviolet (UV) light exposure.

  • Infections (e.g., Epstein–Barr virus).

  • Drugs (drug-induced lupus from hydralazine, procainamide, isoniazid, minocycline, anti-TNF agents).

  • Smoking.

Hormonal Influences

  • Estrogen likely contributes to higher incidence in females.

Pathophysiology

  1. Loss of immune tolerance to self-antigens.

  2. Production of autoantibodies (anti-dsDNA, anti-Smith, anti-Ro, anti-La, antiphospholipid antibodies).

  3. Formation of immune complexes that deposit in tissues.

  4. Activation of complement cascade leading to inflammation and organ damage.

Clinical Features

General Symptoms

  • Fatigue, fever, malaise, weight loss.

Musculoskeletal

  • Symmetrical, non-erosive polyarthritis/polyarthralgia.

Skin and Mucous Membranes

  • Malar rash (“butterfly rash”) sparing the nasolabial folds.

  • Discoid rash.

  • Photosensitivity.

  • Oral/nasal ulcers.

Renal

  • Lupus nephritis: proteinuria, hematuria, hypertension, renal impairment.

Neurological

  • Seizures, psychosis, cognitive dysfunction, peripheral neuropathy.

Cardiovascular

  • Pericarditis, myocarditis, Libman–Sacks endocarditis.

Pulmonary

  • Pleuritis, interstitial lung disease, pulmonary hypertension.

Hematologic

  • Anemia, leukopenia, lymphopenia, thrombocytopenia.

Diagnosis

Clinical Evaluation

  • Diagnosis is based on a combination of clinical features and immunological criteria.

Laboratory Tests

  • Antinuclear antibody (ANA): positive in >95% of cases (screening test).

  • Anti-dsDNA and anti-Smith antibodies: highly specific for SLE.

  • Complement levels (C3, C4): often reduced during flares.

  • ESR often elevated; CRP may be normal unless infection present.

  • Urinalysis for renal involvement.

Classification Criteria

  • 2019 EULAR/ACR criteria: ANA positivity plus additive weighted clinical and immunologic criteria.

Management

Management aims to control disease activity, prevent flares, and limit organ damage.

1. General Measures

  • Sun protection: SPF ≥50, protective clothing.

  • Smoking cessation.

  • Vaccinations (non-live vaccines during immunosuppression).

2. Pharmacologic Treatment

First-Line for All Patients

  • Hydroxychloroquine:

    • Dose: 200–400 mg orally daily.

    • Reduces flares, improves survival, protects against organ damage.

    • Ophthalmologic screening recommended due to risk of retinal toxicity.

Glucocorticoids

  • For acute flares or organ-threatening disease.

  • Prednisolone: 5–15 mg daily for mild/moderate disease; up to 1 mg/kg/day for severe disease, tapered as soon as possible.

  • IV methylprednisolone (500–1000 mg daily for 3 days) for severe organ involvement (e.g., nephritis, CNS lupus).

Immunosuppressants (for steroid-sparing effect or severe disease)

  • Azathioprine: 1–3 mg/kg/day orally.

  • Methotrexate: 7.5–25 mg once weekly orally or subcutaneously (folic acid supplementation needed).

  • Mycophenolate mofetil: 2–3 g/day orally in divided doses (especially for lupus nephritis).

  • Cyclophosphamide:

    • IV pulses: 500–1000 mg/m² monthly for 6 months, then maintenance every 3 months.

    • Used for severe organ-threatening lupus.

Biologic Agents

  • Belimumab: 10 mg/kg IV every 2 weeks for 3 doses, then every 4 weeks (B-lymphocyte stimulator inhibitor).

  • Rituximab: 375 mg/m² weekly for 4 weeks or 1 g IV on days 1 and 15 (used off-label for refractory cases).

3. Organ-Specific Management

Lupus Nephritis

  • Induction: mycophenolate mofetil or cyclophosphamide with corticosteroids.

  • Maintenance: azathioprine or mycophenolate mofetil.

Neuropsychiatric Lupus

  • High-dose glucocorticoids ± cyclophosphamide or rituximab.

Cutaneous Lupus

  • Topical corticosteroids (e.g., clobetasol propionate 0.05% for thick plaques; hydrocortisone 1% for face).

  • Topical calcineurin inhibitors (tacrolimus 0.1% ointment, pimecrolimus 1% cream) for steroid-sparing use.

Monitoring

  • Regular clinical assessment and laboratory monitoring (CBC, renal function, urinalysis, complement levels, anti-dsDNA titres).

  • Ophthalmologic exams for patients on hydroxychloroquine.

Prognosis

  • Prognosis improved markedly with early diagnosis and modern therapies.

  • Main causes of mortality: cardiovascular disease, infection, active disease (especially lupus nephritis and CNS involvement).

  • Long-term remission is possible but relapses are common.




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