Alemtuzumab is a highly effective disease modifying therapy (DMT) for relapsing-remitting multiple sclerosis (RRMS). However, its use carries known risk of immune-mediated conditions, including autoimmune thyroid disease, nephropathies, immune thrombocytopenia, acquired hemophilia, and rheumatoid arthritis. Numerous other autoimmune-related adverse effects are rare but have also been reported. We report a case of alemtuzumab-associated cryptogenic organizing pneumonia.

In 2018, she was identified to have persistent perihilar ground-glass infiltrates on CT thorax in the context of developing dyspnea on exertion, pleuritic pain and productive cough. Serologies and repeated bronchoscopies were unremarkable. She underwent lung biopsy which showed evidence of cryptogenic organizing pneumonia. She was started on prednisone which improved her pulmonary symptoms and perihilar infiltrates. Unfortunately, she did not tolerate prednisone taper and developed worsening symptoms and radiographic findings on lower dose of prednisone. Due to concern for worsening lower extremity edema and obesity, she was eventually transitioned from prednisone to mycophenolate mofetil. From a RRMS standpoint, she remained relapse-free following alemtuzumab and was not treated with additional DMT.

We present a rare, non-infectious steroid-responsive lung disorder following alemtuzumab administration.  While autoimmunity is common following alemtuzumab treatment, delayed onset cryptogenic organizing pneumonia has not been reported with its use in the literature.