A 30 year old women comes to doctor with progressively worsening SOB and dry cough. CXR shows hilar lymphadenopathy and diffuse abnormalities of lung parenchyma. Biopsy specifmen of lung shows nocaseating granuloma. Acid-fast, silve and periodic acid Schif stains of granuloma are negative. 1. What is the likely pathology? 2. Why do you suspect this? 3. What does acid-fast test for? 4. What does silver stain and periodic acid-schiff test for? 5. What physiological feature of the lung is most likely increased in this pathology and why?

The main function of the respiratory system is gas exchange (O2 and CO2). Ventilation is the movement of air through the respiratory tract into (inspiration) and out of (expiration) the respiratory zone (lungs).