Farmer's Lung Disease. A Review

Farmer's lung disease (FLD) is a form of hypersensitivity pneumonitis (HP) caused by inhaling microorganisms from hay or grain stored in conditions of high humidity in the agricultural workplace. It is probably underdiagnosed, especially in northern Spain, where climatic conditions favor the development of this disease. According to previous studies, the most common antigens are usually thermophilic actinomycetes and fungi. The epidemiology of the disease is not well known, and is based on studies conducted by Central European and Asian groups. The clinical presentation may vary, differentiating the chronic (exposure to lower concentrations of the antigen over a longer period time) and the acute forms (after exposure to high concentrations of the antigen). In patients with respiratory symptoms and agricultural occupational exposure, radiological, lung function and/or anatomical pathology findings must be compatible with FLD, bronchoalveolar lavage must show lymphocytosis, and tests must find sensitivity to the antigen. The main treatment is avoidance of the antigen, so it is essential to educate patients on preventive measures. To date, no controlled studies have assessed the role of immunosuppressive therapy in this disease. Corticosteroid treatment has only been shown to accelerate resolution of the acute forms, but there is no evidence that it is effective in preventing disease progression in the long-term or reducing mortality.