Arthus phenomenon

Arthus Phenomenon is a localized hypersensitivity reaction that occurs in the skin following repeated injection of foreign substances. Named after the French scientist Maurice Arthus, who first described it in 1903, the Arthus phenomenon is a type III hypersensitivity reaction, also known as an immune complex-mediated hypersensitivity reaction.

Mechanism

The Arthus phenomenon occurs when an individual is repeatedly exposed to a specific antigen. This repeated exposure leads to the production of high levels of IgG antibodies. When the antigen is introduced again, it binds with these antibodies to form immune complexes. These immune complexes are deposited in the walls of the local blood vessels, leading to an inflammatory response.

The inflammatory response is characterized by the activation of complement, which leads to the recruitment of neutrophils. These neutrophils release lysosomal enzymes and reactive oxygen species, causing tissue damage and necrosis.

Clinical Manifestations

The Arthus phenomenon is characterized by the development of a localized area of erythema and induration, which may be followed by necrosis. The reaction typically occurs within 4 to 12 hours after the injection of the antigen. The most common sites for the Arthus reaction are the skin and the subcutaneous tissues, but it can also occur in other organs such as the lungs and the kidneys.

Diagnosis and Treatment

The diagnosis of the Arthus phenomenon is primarily based on the clinical presentation and the history of repeated exposure to a specific antigen. The treatment involves the avoidance of the offending antigen. In severe cases, corticosteroids may be used to reduce inflammation.

See Also

• Hypersensitivity
• Type III hypersensitivity
• Immune complex
• Complement system
• Neutrophils