Successful etanercept treatment of constrictive pericarditis complicating rheumatoid arthritis.

intensify the pulmonary toxicity of MTX is unclear. RA itself can also affect the lung [6] usually leading to an interstitial pneumonia, either lymphocytic or chronic non-specific with various degrees of organizing pneumonia. None of these features was seen in the presented case. UIP and non-specific interstitial pneumonia (NSIP) could be ruled out as well. Also, the process did not fulfil the criteria of organizing pneumonia. With respect to the aetiology of DAD, infectious organisms could be ruled out by clinical investigation and special stains in tissue sections. With regard to the clinical history, MTX and leflunomide stand out. MTX can cause DAD and later on organizing DAD. The reactive proliferation seen in pneumocytes and bronchiolar cells is quite characteristic. Little is known about the pulmonary side effects of leflunomide. As there are many effects described, such as inhibition of inducible nitric oxide synthase (iNOS), prostaglandin E2 and matrix-metalloproteinase 1, but also an increase of TGF1 [7], leflunomide might cause pulmonary DAD and fibrosis as well. Thus lung biopsy cannot differentiate between MTX or leflunomide pneumonitis, but supports the theory of drug-induced pneumonitis. From the clinical point of view the most reliable trigger in our patient is the leflunomide therapy. Though there are reports where pneumonitis occurred after discontinuation of MTX [8] a period of 3 months is too long to claim MTX as the only responsible drug. However, it remains unclear if the initial MTX therapy has increased the patient’s risk of developing pneumonitis. The long elimination half-life of approximately 2 weeks makes a suspected leflunomide pneumonitis even more dangerous. It is therefore important to remember that leflunomide therapy can possibly cause life-threatening pneumonitis. Immediate drug elimination using charcoal or cholestyramin should be considered in any case presenting with pulmonary symptoms. In addition the use of leflunomide should be carefully considered in patients with pre-existing lung disease or combined MTX therapy.