FEATURE
DETAIL
MECHANISM
CLASSIC CLUE
Women of childbearing age (~9:1); more frequent and severe in Black and Hispanic patients.
Genes + hormones + UV light + infections
Flares with sun exposure, pregnancy
Pathogenesis
why antibodies form
Apoptotic debris is cleared poorly → nuclear antigens exposed → autoantibodies.
Early complement deficiency (C1q, C2, C4) impairs clearance · type III > type II injury
↓ C3, C4 in active disease
Malar rash sparing nasolabial folds, discoid rash, photosensitivity, painless oral ulcers, nonerosive arthritis.
Immune complexes at the dermal–epidermal junction
Butterfly rash after sun
Diffuse proliferative GN (most common, most severe, nephritic) or membranous (nephrotic).
Subendothelial deposits → wire-loop capillaries
Leading cause of death with infection and cardiovascular disease
Autoimmune hemolytic anemia, leukopenia, thrombocytopenia; anemia of chronic disease.
Type II antibodies against blood cells
Coombs⁺ hemolysis in a young woman
Pleuritis, pericarditis; Libman-Sacks endocarditis; accelerated atherosclerosis; seizures, psychosis.
Sterile vegetations on both sides of the mitral valve
Pleuritic chest pain + rash + arthritis
Drug-induced lupus
reversible
Hydralazine, procainamide, isoniazid, minocycline, quinidine, TNF inhibitors; more likely in slow acetylators.
Antihistone antibodies; kidneys and CNS usually spared
Resolves after stopping the drug
Antiphospholipid syndrome
primary or with SLE
Recurrent arterial or venous thrombosis and recurrent pregnancy loss.
Lupus anticoagulant, anticardiolipin, anti-β₂-glycoprotein I
Prolonged PTT not corrected by mixing; false-positive VDRL; anticoagulate
Neonatal lupus
passive transfer
Maternal IgG anti-Ro/SSA crosses the placenta.
Damages fetal conduction tissue
Congenital complete heart block, neonatal rash
Hydroxychloroquine for nearly all; steroids for flares; mycophenolate or cyclophosphamide for nephritis.
Sun protection
Hydroxychloroquine → retinal screening