Give an overview.
Type III hypersensitivity reactions, also referred to as immune complex reactions, are antibody-mediated.
Clinical features, diagnostics, and treatment depend on the underlying etiology (see “Hypersensitivity classification” above).
Distribution of disease: systemic
Describe the pathophysiology.
Antigen (e.g., the molecules of a drug in circulation) binds to IgG to form an immune complex (antigen-antibody complex)
Immune complexes are deposited in tissue, especially blood vessels → initiation of complement cascade → release of lysosomal enzymes from neutrophils → cell death → inflammation → vasculitis
Drug-induced hypersensitivity vasculitis
Systemic lupus erythematosus (e.g., lupus nephritis, hypertension, thrombosis)
Serum sickness and serum sickness-like reactions