Hypersensitivity pneumonitis (HP) is a pulmonary disease with symptoms of dyspnea and cough resulting from the inhalation of an antigen to which the patient has been previously sensitized. HP is an orphan disease, and current concepts on its diagnosis and management are often outdated. The objectives of this review are to summarize the modern evidence regarding the diagnostic criteria of HP, its pathophysiology, the procedures involved in the management of the disease, and its treatment strategies. Several areas for further research are identified, with priority given to (1) the establishment of a multicenter collaborative network to enhance the recognition, diagnosis, and management of the disease; (2) the development and support of population-based studies to provide additional insights into environmental and clinical characterization of HP; and (3) the exploration of the use and validity of biomarkers of both exposure and disease.

Conventional asthma and COPD treatments include the use of bronchodilators, mainly β2-adrenergic agonists, muscarinic receptor antagonists and corticosteroids or leukotriene antagonists as anti-inflammatory agents. These active drugs are administered either separately or given as a fixed-dose combination medication into a single inhaler. ASM-024, a homopiperazinium compound, derived from the structural modification of diphenylmethylpiperazinium (DMPP), has been developed to offer an alternative mechanism of action that could provide symptomatic control through combined anti-inflammatory and bronchodilator properties in a single entity. A dose-dependent inhibition of cellular inflammation in bronchoalveolar lavage fluid was observed in ovalbumin-sensitized mice, subsequently treated for 3 days by nose-only exposure with aerosolized ASM-024 at doses up to 3.8 mg/kg (ED50 = 0.03 mg/kg). The methacholine ED250 values indicated that airway hyperresponsivenness (AHR) to methacholine decreased following ASM-024 administration by inhalation at a dose of 1.5 mg/kg, with a value of 0.145±0.032 mg/kg for ASM 024-treated group as compared to 0.088±0.023 mg/kg for untreated mice. In in vitro isometric studies, ASM-024 elicited dose-dependent relaxation of isolated mouse tracheal, human, and dog bronchial preparations contracted with methacholine and guinea pig tracheas contracted with histamine. ASM-024 showed also a dose and time dependant protective effect on methacholine-induced contraction. Overall, with its combined anti-inflammatory, bronchodilating and bronchoprotective properties, ASM-024 may represent a new class of drugs with a novel pharmacological approach that could prove useful for the chronic maintenance treatment of asthma and, possibly, COPD.

Farmer's lung is an important form of hypersensitivity pneumonitis. It is believed to represent a delayed type allergic reaction to microorganisms found in moldy hay dust. The disease is prevalent in farmers from countries where, because of high humidity in the summer, molding of stored hay is unavoidable.

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