Hypersensitivity pneumonitis is classically a/an: (A) Allergic reaction, (B) Type II hypersensitivity, (C) Immune complex mediated hypersensitivity, (D) Cell mediated hypersensitivity
Answer is C. Hypersensitivity pneumonitis Allergic alveolitis TYPE III +TYPE IV HS Complement & Ig in the vessel walls - Type III Non-caseating granulomas in 2/3rd patients - Type IV