Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) – Study Guide for Medical Students

Definition

Systemic lupus erythematosus (SLE) is a chronic, multisystem autoimmune disease characterized by loss of self-tolerance, production of diverse autoantibodies (notably ANA and anti–double-stranded DNA), formation of immune complexes, and resultant complement-mediated tissue inflammation. It can involve the skin, joints, kidneys, hematologic system, cardiovascular system, lungs, and central nervous system and follows a relapsing–remitting course with variable severity.[1]

Epidemiology

SLE occurs worldwide and affects all ethnicities, but with marked variation in prevalence and severity.

• Sex: Strong female predominance (≈9:1 female:male), particularly in women of childbearing age due to hormonal and immunologic influences.[2]
• Age: Peak incidence in 15–45 years, though childhood- and late-onset SLE also occur.
• Ethnicity: Higher prevalence and more severe disease in people of African, Hispanic/Latino, Asian, and Indigenous descent compared with White populations.[1]
• Genetic risk: Multiple susceptibility loci, including variants in immune-regulatory genes such as IL7RA, contribute to disease risk and phenotype.[5]
• Burden: SLE is associated with significant morbidity, early organ damage, impaired quality of life, and increased mortality compared with the general population.[1]

Pathophysiology

SLE results from a complex interplay of genetic susceptibility, environmental triggers, hormonal factors, and immune dysregulation leading to loss of self-tolerance and immune complex–mediated tissue injury.

• Genetic predisposition: Multiple genes involved in innate and adaptive immunity (e.g., HLA class II, complement components, IL7RA) increase risk. Variants in IL7RA can alter IL-7 receptor alpha function, impacting T-cell homeostasis and autoimmunity.[5]
• Defective clearance of apoptotic cells: Impaired clearance leads to the persistence of apoptotic debris, exposing nuclear antigens and promoting autoantibody formation.[3]
• Loss of self-tolerance: Abnormal B-cell and T-cell selection and regulation allow autoreactive clones to survive and expand, with help from follicular helper T cells and cytokines (e.g., BAFF).
• Autoantibody production: B cells produce a broad array of autoantibodies (ANA, anti-dsDNA, anti-Sm, antiphospholipid antibodies). These antibodies may directly damage cells or form circulating immune complexes.
• Immune complex deposition: Immune complexes deposit in small vessels and tissues (kidney glomeruli, skin, joints, CNS), activating complement and recruiting inflammatory cells, causing vasculitis and organ injury.[1]
• Complement activation: Classical pathway activation leads to consumption of complement components (low C3, C4), which is both a marker and driver of disease activity.
• Cytokine milieu: Type I interferons, IL-6, IL-17, and other cytokines are upregulated and perpetuate chronic inflammation and B-cell activation.

Clinical Presentation

SLE has a highly heterogeneous clinical presentation. Patients may present with isolated organ involvement or with classic multisystem disease. Symptoms often wax and wane, with periods of flare and remission.

General and Constitutional Features

• Fatigue: Very common and often debilitating, even with low disease activity.
• Fever: Low-grade fevers are typical during flares, after exclusion of infection.
• Weight changes: Weight loss during active disease or weight gain from glucocorticoid therapy.
• Malaise and myalgias: Common nonspecific complaints.

Mucocutaneous Manifestations

• Malar rash: Fixed erythema over the cheeks and nasal bridge, classically sparing the nasolabial folds.
• Discoid rash: Erythematous, scaly plaques with follicular plugging, leading to scarring and dyspigmentation.
• Photosensitivity: Exaggerated skin reaction to ultraviolet light, often triggering flares.
• Oral/nasal ulcers: Typically painless, shallow ulcers on the hard palate or nasal mucosa.
• Alopecia: Non-scarring alopecia with active disease; scarring alopecia in discoid lesions.

Musculoskeletal Manifestations

• Arthralgia and arthritis: Symmetric, non-erosive inflammatory arthritis involving small joints of hands, wrists, and knees is common.
• Jaccoud arthropathy: Deforming, non-erosive arthropathy with ligament laxity and reducible joint deformities.
• Myositis: Less common; can present with proximal muscle weakness and elevated muscle enzymes.

Renal Manifestations

Renal involvement (lupus nephritis) is a major determinant of morbidity and prognosis.

• Clinical features: Asymptomatic proteinuria and microscopic hematuria are common; some patients develop nephritic or nephrotic syndrome and progressive renal insufficiency.
• Classification: WHO/ISN–RPS classes I–VI lupus nephritis (e.g., class III/IV proliferative, class V membranous) guide prognosis and treatment.
• Monitoring: Regular urine protein quantification (spot protein/creatinine ratio or 24-h collection) and serum creatinine are essential.[1]

Hematologic Manifestations

• Anemia: Anemia of chronic disease, iron deficiency, or autoimmune hemolytic anemia.
• Leukopenia/lymphopenia: Common finding, often correlating with disease activity.
• Thrombocytopenia: Immune-mediated, may mimic ITP and can be severe.
• Antiphospholipid antibodies: Can coexist, conferring thrombotic and obstetric complications (antiphospholipid syndrome).[3]

Cardiovascular and Pulmonary Manifestations

• Pericarditis: The most common cardiac manifestation; presents with pleuritic chest pain and friction rub.
• Myocarditis: Can contribute to heart failure and arrhythmias.
• Libman–Sacks endocarditis: Sterile vegetations, typically on mitral or aortic valves, associated with embolic risk.
• Accelerated atherosclerosis: Premature coronary artery disease due to chronic inflammation and steroid use.
• Pleuritis and pleural effusions: Common respiratory manifestations.
• Interstitial lung disease and pulmonary hypertension: Less common but important for prognosis.

Neuropsychiatric Manifestations

• CNS involvement: Seizures, psychosis, stroke, transverse myelitis, cognitive dysfunction, and headaches.
• Peripheral nervous system: Peripheral neuropathies, mononeuritis multiplex.
• Psychological/sexual health impact: Chronic disease, pain, fatigue, and medication side effects contribute to depression, anxiety, and sexual dysfunction, particularly in women of reproductive age.[2]

Other Organ Systems

• Gastrointestinal: Abdominal pain, mesenteric vasculitis, pancreatitis, hepatomegaly, and rarely protein-losing enteropathy.
• Ocular: Keratoconjunctivitis sicca (secondary Sjögren), retinal vasculitis, optic neuritis.
• Dermatologic vasculitis and ulcers: Including rare associations with pyoderma gangrenosum in complex cases.[3]

Diagnosis

Diagnosis of SLE is based on a combination of clinical features and immunologic findings, after exclusion of alternative causes such as infection, malignancy, and other autoimmune diseases.

Classification Criteria (for research and high-yield exam reference)

Contemporary classification systems (e.g., EULAR/ACR) use weighted clinical and immunologic criteria with a positive ANA as an entry criterion. In practice, medical students should recognize common clusters of features rather than memorize all weights.

• Entry criterion: Positive ANA at a titer (e.g., ≥1:80 by immunofluorescence).
• Clinical domains: Constitutional, hematologic, neuropsychiatric, mucocutaneous, serosal, musculoskeletal, renal.
• Immunologic domains: Specific autoantibodies (anti-dsDNA, anti-Sm, antiphospholipid) and low complement (C3, C4).

Key Laboratory Tests

• Antinuclear antibody (ANA): Highly sensitive but nonspecific screening test; usually positive in SLE.
• Anti–double-stranded DNA (anti-dsDNA): Relatively specific for SLE and correlates with disease activity and lupus nephritis.[1]
• Anti-Smith (anti-Sm): Highly specific but less sensitive; a strong supportive marker for SLE.
• Antiphospholipid antibodies: Lupus anticoagulant, anticardiolipin, and anti–β2 glycoprotein I antibodies indicate risk of thrombosis and pregnancy morbidity.[3]
• Complement levels: Low C3 and C4 often indicate active disease, especially nephritis.
• CBC: Evaluates anemia, leukopenia, and thrombocytopenia.
• Renal function and urinalysis: Serum creatinine, eGFR, urine protein, sediment (casts, hematuria) for lupus nephritis screening and monitoring.
• ESR/CRP: ESR often elevated in active SLE; CRP may be normal or mildly elevated unless there is serositis or infection.

Imaging and Biopsy

• Renal biopsy: Recommended in significant proteinuria or declining renal function to classify lupus nephritis (class I–VI), assess activity vs chronicity, and guide therapy.[1]
• Neuroimaging: MRI brain/spine for suspected CNS involvement (stroke, myelitis, aseptic meningitis).
• Echocardiography: To assess pericardial effusion, myocarditis, or Libman–Sacks endocarditis.
• Skin biopsy: Interface dermatitis with immune complex deposition at the dermoepidermal junction ("lupus band") supports diagnosis of cutaneous lupus.

Management

Management of SLE is individualized based on disease severity, organ involvement, comorbidities, and patient factors. The goals are to control inflammation, prevent organ damage, reduce flares, and improve quality of life while minimizing treatment toxicity.

General Principles

• Education and adherence: Understanding disease and therapy, and promoting adherence is crucial; nonadherence is a major driver of flares and damage, particularly in young adults.[4]
• Sun protection: Use of broad-spectrum sunscreen, protective clothing, and avoidance of intense UV exposure to reduce cutaneous flares.
• Lifestyle modification: Smoking cessation, exercise, weight control, and cardiovascular risk factor management (BP, lipids, diabetes) to mitigate atherosclerosis.
• Vaccination: Age-appropriate immunizations, especially for patients on immunosuppressive therapy (avoid live vaccines when significantly immunosuppressed).

Pharmacologic Therapy

Background Therapy

• Hydroxychloroquine (HCQ):
  • Cornerstone of SLE management for nearly all patients unless contraindicated.
  • Reduces disease activity and flares, protects against organ damage, and improves survival.[1]
  • Requires regular ophthalmologic monitoring for retinal toxicity.

Glucocorticoids

• Indications: Rapid control of moderate to severe disease flares, organ-threatening manifestations (e.g., nephritis, CNS involvement, hemolytic anemia).
• Regimens:
  • Low-dose oral prednisone (e.g., ≤7.5–10 mg/day) for mild disease.
  • Intermediate to high-dose oral regimens for more active disease.
  • Intravenous pulse methylprednisolone for severe or life-threatening manifestations (e.g., rapidly progressive nephritis, CNS lupus).
• Goal: Use the lowest effective dose and taper as quickly as clinically feasible to limit cumulative toxicity.

Immunosuppressive and Immunomodulatory Agents

• Conventional agents:
  • Azathioprine: Used as a steroid-sparing agent and for maintenance, including in lupus nephritis and hematologic disease.
  • Mycophenolate mofetil: Commonly used for induction and maintenance of class III/IV/V lupus nephritis and for some extrarenal manifestations.
  • Cyclophosphamide: Reserved for severe, organ-threatening disease (e.g., severe nephritis, CNS lupus, pulmonary hemorrhage).
  • Methotrexate: Useful as a steroid-sparing agent for musculoskeletal and cutaneous disease.
• Biologic and targeted therapies:
  • Belimumab (anti-BAFF): Approved for active SLE with inadequate response to standard therapy; reduces flares and steroid requirement.[1]
  • Rituximab (anti-CD20): Used off-label for refractory disease, particularly severe hematologic or renal involvement.
  • Other emerging therapies: Modified mesenchymal stem cell therapies and novel biologics targeting key immune pathways are being explored for refractory SLE.[1]

Management of Specific Manifestations

• Cutaneous disease: Topical corticosteroids or calcineurin inhibitors; HCQ as systemic baseline; consider methotrexate, mycophenolate, or other agents for refractory skin disease.
• Musculoskeletal disease: NSAIDs for mild pain (in selected patients), HCQ, low-dose glucocorticoids, and methotrexate as needed.
• Lupus nephritis:
  • Induction: High-dose steroids plus mycophenolate or IV cyclophosphamide for class III/IV; mycophenolate or calcineurin inhibitors for class V with significant proteinuria.
  • Maintenance: Lower-dose steroids plus mycophenolate or azathioprine.
• Neuropsychiatric SLE: High-dose steroids and immunosuppressants for inflammatory manifestations (e.g., myelitis), plus targeted management of seizures, psychosis, or mood disorders.
• Antiphospholipid syndrome (APS): Anticoagulation (e.g., warfarin with target INR typically 2–3) for thrombotic events; low-dose aspirin ± heparin during pregnancy for obstetric APS.[3]

Monitoring and Long-Term Care

• Regular assessments: Follow disease activity, organ involvement, and medication toxicity with periodic clinical evaluation and laboratory tests (CBC, creatinine, urinalysis, complements, anti-dsDNA).
• Damage prevention: Minimize glucocorticoid exposure, manage cardiovascular risk factors, and screen for osteoporosis.
• Adherence strategies: Address barriers to adherence, especially in young adults, through shared decision-making, simplified regimens, and psychosocial support.[4]
• Fertility and pregnancy: Plan pregnancies during disease quiescence, adjust teratogenic medications (e.g., stop mycophenolate, methotrexate), and monitor closely for flares and APS-related complications.

Complications and Prognosis

• Organ damage: Cumulative damage from disease and treatments, especially renal failure, cardiovascular disease, and neuropsychiatric sequelae.
• Infections: Increased susceptibility due to disease-related immune dysfunction and immunosuppressive therapy.
• Osteonecrosis: Particularly multifocal osteonecrosis related to chronic glucocorticoid use; can significantly impair function.[3]
• Cardiovascular disease: Major contributor to late mortality due to accelerated atherosclerosis.
• Malignancy: Slightly increased risk of certain cancers (e.g., lymphoma) in some cohorts, influenced by both disease and treatments.
• Quality of life: Chronic pain, fatigue, sexual dysfunction, mood disorders, and treatment side effects impact physical, emotional, and social well-being.[2]

Key Clinical Pearls for Medical Students

• Think of SLE in young women with multisystem involvement (rash, arthritis, cytopenias, renal abnormalities) and positive ANA.
• ANA is highly sensitive but not specific; anti-dsDNA and anti-Sm are more specific and clinically useful for confirming SLE and tracking nephritis activity.[1]
• Hydroxychloroquine is foundational therapy for nearly all SLE patients and should be continued long term unless contraindicated, with eye monitoring.
• Minimize steroid exposure: Use the lowest effective dose and combine with steroid-sparing agents to prevent long-term damage (osteoporosis, diabetes, CVD, osteonecrosis).
• Always exclude infection before attributing fever, cytopenias, or organ dysfunction to a lupus flare, especially in patients on immunosuppression.
• Renal involvement may be silent; routine urinalysis and renal function tests are essential in all SLE patients.
• Antiphospholipid antibodies in SLE significantly alter thrombotic risk and pregnancy management; remember the association with stroke and recurrent miscarriages.[3]
• Adherence and psychosocial factors are critical drivers of outcomes, particularly among young adults; address fatigue, depression, and sexual health explicitly in assessments.[2][4]
• Emerging therapies including biologics (e.g., belimumab) and modified mesenchymal stem cells reflect the central role of B-cell and cytokine dysregulation in SLE pathogenesis and may shift future management paradigms.[1]

Exam Tips

• On exams, the classic vignette is a young woman with malar rash, photosensitivity, non-erosive arthritis, cytopenias, and renal findings (proteinuria, hematuria) plus positive ANA and anti-dsDNA.
• Distinguish SLE from rheumatoid arthritis by non-erosive arthritis and from drug-induced lupus by antibody profile (anti-histone, usually no anti-dsDNA, less renal/CNS involvement).
• Remember that antimalarials (HCQ) reduce flares and improve survival, and that chronic steroid use is a major cause of long-term complications such as osteonecrosis and osteoporosis.