Synonyms: pulmonary mycotoxicosis, silo-unloader's syndrome
Similarities to hypersensitivity pneumonitis:
(1) There is a latency period of 4 or more hours.
(2) Symptoms include chills, malaise, dry cough, and dyspnea.
(3) Increased numbers of neutrophils in the bronchoalveolar lavage.
(4) Nonsmokers may be at greater risk.
(5) Symptoms usually last 12-36 hours (ODTS can last up to 5 days).
(6) Leukocytosis in peripheral blood.
Differences from hypersensitivity pneumonitis:
(1) It is about 5 times more common in farmers and may occur in patient clusters.
(2) It is more common in summer and fall (versus winter and early spring).
(3) Severe hypoxemia does not occur (may show normal oxygenation to mild hypoxemia).
(4) Prior sensitization to antigens usually does not occur, with serology tests usually negative.
(5) There are no sequelae of physiologic significance.
(6) Symptoms may include nausea, myalgia, chest tightness and headache (flu-like).
(7) Chest auscultation is normal or may show scattered rales (vs end-inspiratory bibasilar rales).
(8) No or mild restriction on spirometry (vs moderate to severe in hypersensitivity pneumonitis).
(9) The chest X-ray does not show infiltrates. Minimal interstitial infiltrates may be present.
(10) Lung biopsy shows multifocal acute inflammation of terminal bronchioles, in alveoli and interstitial area. Intra-alveolar exudate consists of neutrophils and macrophages. Large numbers of fungal spores may be present.
Limitations:
• Serologic tests are helpful if negative. It is important to try to identify an allergen in the environment to compare any antibodies against, since a person may have antibodies against unrelated environmental agents.
