Description

• Multisystem autoimmune inflammatory disorder with variable presentation, disease course, and prognosis
• May manifest in any organ system, especially dermatologic, renal, hematologic, musculoskeletal, cardiovascular, pulmonary, immunologic, and reproductive
• Synonyms: systemic lupus erythematosus (SLE), lupus

Epidemiology

Incidence

• Overall incidence in United States is 5 to 7 per 100,000 person-years.
• Significant variation based on ethnicity: black 16.0, American Indian/Alaska Native 7.4, Hispanic 5.6, Asian/Pacific Islander 4.6, white 3.3 per 100,000 person-years
• Strong female predominance compared to male: 9.8 versus 0.8 per 100,000 person-years (about 12-fold higher)
• Peak incidence in females ranges from 3rd to 7th decades of life.
• Peak incidence in males later, from 5th to 7th decades of life

Prevalence

• Overall prevalence in United States ranges from 70 to 100 cases per 100,000.
• Increasing due to better recognition and increased survival
• Highest prevalence in black women: 498 per 100,000
• Strong female predominance compared to male: 179 versus 21 cases per 100,000 (about 9-fold higher)

Etiology and Pathophysiology

Complex and multifactorial: Genetic, environmental, immunoregulatory, hormonal, and epigenetic factors all play a role in pathogenesis.

Genetics

• More than 30 susceptibility loci for SLE in genome-wide association studies
• Heritability, the proportion of phenotypic variance explained by genetics, between 40% and 70%
• Previous criteria from American College of Rheumatology (ACR) and Systemic Lupus International Collaborating Clinics (SLICC) still used widely in clinical practice

Risk Factors

• Ethnicity: highest risk in black populations; intermediate risk in Asian, Hispanic, and American Indian/Alaska Native populations
• Hormonal: female sex, early menarche, endometriosis, surgical menopause, earlier age at menopause
• Family history of SLE or other autoimmune disease
• Environmental: cigarette smoking, crystalline silica exposure, exogenous female hormones, certain medications (drug-induced lupus)

Commonly Associated Conditions

• Antiphospholipid syndrome
• Depression
• Fibromyalgia
• Thyroid disease
• Overlap connective tissue disease syndromes: rheumatoid arthritis (RA), Sjögren syndrome, systemic sclerosis, polymyositis, dermatomyositis