Final answer:
Hypersensitivity involves excessive immune responses to substances, potentially resulting in conditions like contact dermatitis. Autoimmunity is a hypersensitivity to self antigens, causing diseases such as lupus and rheumatoid arthritis. Discoid lupus is a skin-specific autoimmune disease causing coin-shaped lesions.
Step-by-step explanation:
Understanding Hypersensitivity and Autoimmunity
Hypersensitivity refers to the excessive or pathologic immune responses to antigens, including allergens. This can manifest in various forms, one of which is delayed hypersensitivity, where exposure to substances such as nickel or poison ivy can cause local inflammation. Types of hypersensitivity include contact dermatitis and the tuberculin reaction.
Autoimmunity is an erroneous hypersensitivity reaction to self antigens, leading to autoimmune diseases. In these cases, autoantibodies mistakenly target the body's own tissues, as seen with diseases like type I diabetes mellitus, multiple sclerosis, and rheumatoid arthritis. Systemic lupus erythematosus is a prime example of a diffuse autoimmune disease, affecting multiple tissues and organs, often treated with immunosuppressive and anti-inflammatory drugs.
Discoid lupus is a particular form of chronic cutaneous lupus erythematosus that presents itself with coin-shaped lesions on the skin, which can lead to scarring. This is another aspect of autoimmune response, where the immune system attacks the skin, specifically.