History and exam

Key diagnostic factors

common

flu-like illness with low-grade fever, fatigue, and arthralgia

Common with cryptogenic OP.

Symptoms last for several days, typically <2 months.

Other diagnostic factors

common

cough

Cough is usually mild with no sputum production.

shortness of breath

Not a feature early in the disease but develops as OP becomes involved with the lung parenchyma.

bilateral crackles

End-inspiratory bilateral crackles occur in up to 80% of patients with OP.

Wheezes do not occur.

Risk factors

strong

infectious pneumonia

OP may occur after infectious pneumonias. Organisms include viral agents, bacterial agents, atypical organisms, and parasites.[10]

connective tissue diseases

OP may occur in association with all of the connective tissue disorders, including rheumatoid arthritis, lupus erythematosus, polymyositis and dermatomyositis, Sjogren syndrome, mixed connective tissue, and antiphospholipid syndrome.[13][14] In some situations, the drug used for treating the connective tissue disease can also cause OP (e.g., gold or methotrexate for treatment of rheumatoid arthritis).

immunologic diseases and inflammatory bowel disease

OP occurs in association with immunologic diseases such as common variable immunodeficiency syndrome and inflammatory bowel disease. Sulfasalazine used for treatment of inflammatory bowel disease may also cause OP.

organ transplantation

OP can occur in up to 10% of lung and bone marrow transplant recipients.[16][17] OP has been reported in liver and kidney recipients.

medication use

Over 30 medications can cause OP, including antibiotics, cardiovascular drugs (e.g., amiodarone), cancer chemotherapy drugs (e.g., bleomycin), anti-inflammatory agents, immunosuppressive agents, and anticonvulsants.

breast radiation therapy

OP following breast radiation therapy may occur in 1% to 3% of patients and may resolve without corticosteroid treatment.[19][20][21][22]

exposure to toxins

Documented reports of OP caused by occupational or environmental toxic exposure are rare. Textile printing dye has been the most well documented, and others include Penicillium mold dust, house fire, food spice processing, and paraffin mineral oil.[23][24][41]

weak

vaping

Many of the flavoring agents in e-liquids have been associated with sporadic case reports of lung injury, including OP, due to e-cigarette or vaping product use.[25]​ The pattern of acute lung injury is typical of OP, diffuse alveolar damage, or both.[25]​

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