Cervical lymphadenitis caused by Mycobacterium avium in a patient treated with Janus kinase inhibitors

A woman diagnosed with rheumatoid arthritis and treated with Janus kinase (JAK) inhibitors presented with a gradually enlarging bilateral submandibular lymph nodes swelling that had lasted several weeks. A lymph node biopsy showed epithelioid granulomatous lymphadenitis with caseous necrosis. Mycobacteria grew in acid-fast bacteria culture and were identified as Mycobacterium avium by polymerase chain reaction. The patient was diagnosed with cervical lymphadenitis caused by M. avium. A computed tomography scan showed no evidence of a mass or infection at other sites, including the lungs; therefore, the mass was excised without any antimicrobial treatments. Her neck mass had not recurred at 9 months after the excision. JAK inhibitors have emerged as an important new class of oral therapy for rheumatoid arthritis and other diseases. Physicians should be aware of the relatively rare complications, such as cervical lymphadenitis caused by nontuberculous mycobacteria, when using JAK inhibitors.