What is the difference between acute and chronic form of hypersenstivity pneumonitis

Acute form : Produces dry cough and breathlessness on exertion CXR findings – micro-nodularity denser towards the hilar Chronic form : Long-term exposure to antigens over months or years malaise (feeling persistently unwell) dry cough and breathlessness CXR findings → normal but may progress to pulmonary fibrosis affecting upper zones