Fibrotic hypersensitivity pneumonitis

Fibrotic hypersensitivity pneumonitis (FHP) is a specific form of HP defined by chest imaging evidence or pathologic evidence of fibrosis or scarring. Fibrotic HP appears to be irreversible, is often progressive and frequently indistinguishable from other forms of chronic fibrosing interstitial lung diseases (ILD), in particular idiopathic pulmonary fibrosis (IPF). Accurate diagnosis is a challenge given the diverse and often nonspecific clinicoradiologic patterns, heterogenous clinical course, and a frequent lack of a readily recognizable temporal relationship between exposure to an inciting antigen (IA) and symptoms in more than half of the patients. This chapter focuses on the clinical features, diagnostic evaluation and management of FHP.