Sarcoidosis or extrinsic allergic alveolitis?

Of 46 patients with sarcoidosis, there was an exposure to type III allergens in 14 subjects. On closer examination of 2 patients diagnosed as having sarcoidosis there were distinct features suggesting farmer's lung too. Inhalative challenge recording airway resistance, CO transfer factor and other clinical features confirmed farmer's lung disease in these patients. Because there are sometimes poor clinical and uncertain histological differences, inhalative challenge is considered an important diagnostic procedure to differentiate hypersensitivity pneumonitis from sarcoidosis.