LAUSR

Dear Editor, Methotrexate (MXT) is an immunosuppressant folic acid antagonist medication, often used by dermatologists for psoriasis and other skin conditions (Hammerschmidt & Brenner, 2014). MTX-induced pneumonitis (MIP) is an uncommon adverse reaction of MXT. Most frequent within the first year of treatment (Saravanan & Kelly, 2003). In a review of 189 cases of MIP, rheumatoid arthritis was the most frequent underlying disease (53%), but psoriasis/psoriatic arthritis (Ps) was identified in 8% of cases. Patients with rheumatoid arthritis may be more susceptible to MIP (Zisman, McCune, Tino, & Lynch, 2001). Salehi, Miller, and Khaing (2017) recently reported a case of MIP in a 77-yearold woman treated for rheumatoid arthritis. The patient was on MTX 2.5 mg administered orally, in a daily dose for over 30 years. Though the patho-mechanism MIP is unclear, it is considered an idiosyncratic immune reaction (Phillips, Jones, & Baker, 1987; Saravanan & Kelly, 2003). The risk increases in those >60 years, with hypoalbuminemia, diabetes, and on daily dosing as opposed to weekly (Hilliquin, Renoux, Perrot, & Menkès, 1996). The best approach of MTX-induced lung toxicity would be to combine the clinical, laboratory, and radiologic findings (although, chest-x ray may be normal in some cases) together to have an appropriate management plan. This would include ruling out acute infections, a trial of MTX discontinuation, empiric antimicrobial therapy at likely pathogens until the definitive procedures and cultures are performed and treatment with high-dose steroids, especially when a patient is not severely sick (Salehi et al., 2017). Interestingly, up to 50% of patients with subacute onset of MTX lung toxicity demonstrate peripheral eosinophilia, which strongly supports the diagnosis when present (Hilliquin et al., 1996). With the combination of dyspnea, a history of MTX intake, upper lobe infiltrates on imaging studies and most important, eosinophilia, dermatologist should consider MTX-induced lung toxicity on the top of the differential diagnosis (Salehi et al., 2017).