Which of the following would be considered an organ-specific autoimmune disease?

• A. Systemic lupus erythematosus (SLE)
• B. Rheumatoid arthritis (RA)
• C. Granulomatosis with polyangiitis (GPA)
• D. Hashimoto's thyroiditis

Answer: (D)

Organ-specific autoimmune diseases are scenarios where the immune system targets antigens confined to a single organ, causing damage mainly in that organ. Hashimoto’s thyroiditis is a classic example: autoantibodies against thyroid antigens such as thyroid peroxidase and thyroglobulin, along with T-cell–mediated destruction, lead to chronic lymphocytic infiltration and loss of thyroid function. This primarily affects the thyroid with little direct involvement of other organs.

The other conditions involve broader, multi-organ involvement. Systemic lupus erythematosus has autoantibodies against nuclear components that affect skin, kidneys, joints, and more. Granulomatosis with polyangiitis is a systemic vasculitis impacting the lungs, kidneys, sinuses, and other sites. Rheumatoid arthritis mainly targets joints but can have systemic features as well, rather than being confined to a single organ.