Hypersensitivity pneumonitis, also called extrinsic allergic alveolitis, is a complex syndrome of varying intensity, clinical presentation, and natural history, rather than a single uniform disease. Hypersensitivity pneumonitis (HP) is characterized by diffuse inflammation of lung parenchyma and airways in previously sensitized patients. Based on the length and intensity of exposure and subsequent duration of illness, clinical presentations of HP are categorized as acute, subacute (intermittent), and chronic progressive. PathCon conducted several investigations of hypersensitivity Pneumonitis (HP) in machine workers exposed to metalworking fluids. These case studies of HP showed potentially high exposures to a rare and newly discovered species of Mycobacterium. PathCon can be a great resource in evaluating potential exposure to hypersensitivity pneumonitis.