Leflunomide induced acute interstitial pneumonia

Leflunomide induced acute interstitial pneumonia is a form of drug induced interstitial lung disease. The precipitation of radiological evidence of pulmonary infiltrates, clinical acute respiratory illness in the context of a good temporal relationship with commencement of the agent and no clear evidence of precipitating infection could suggest the diagnosis.

Pathology

Leflunomide (or Arava) is a disease-modifying anti-rheumatic drug (DMARD) that is used in patients with rheumatoid arthritis (RA). Patients can get an acute deterioration of symptoms which can clinically progress like an acute interstitial pneumonitis.

Treatment and prognosis

The overall prognosis is variable with some cases even reported as being fatal . Agents such as prednisolone (pulse therapy) and cholestyramine have been used and prompt treatment with cessation of agent may improve overall prognosis.

Differential diagnosis

On imaging possible differential considerations include

• sudden rapid progression of preexisting interstitial fibrosis in rheumatoid disease
• concurrent complicating multifocal infective process such as pneumocystis pneumonia  or mycoplasma pneumonia etc.