A case of extrapulmonary tuberculosis after use of baricitinib.

Extrapulmonary tuberculosis (TB) can occur in patients treated with Janus kinase (JAK) inhibitors. We present a case of rheumatoid arthritis complicated by extrapulmonary TB following baricitinib treatment. A 45-year-old Japanese woman was diagnosed with rheumatoid arthritis at another hospital, and she subsequently started treatment with methotrexate (MTX) at 6.0 mg/week and prednisolone at 3.0 mg/day at our institute. The MTX dose was increased to 10 mg/week, and clinical remission was achieved; however, the disease activity flared up 6 months after the initial visit. Isoniazid (INH) prophylaxis was started following positive T-SPOT® screening for TB, and baricitinib (Olumiant®) was introduced 3 weeks later because of an insufficient response to MTX. INH prophylaxis was continued for 6 months. Ten months after starting INH treatment, a painless mass was observed on the left side of the patient's neck. Magnetic resonance imaging showed enlarged lymph nodes with calcification. A subsequent biopsy and pathologic examination led to a diagnosis of tuberculous lymphadenitis, and the patient was started on anti-TB therapy. Ten months later, the patient was still in remission and doing well. Extrapulmonary TB can be difficult to diagnose because of inconsistent physical and laboratory findings. When treating patients with JAK inhibitors, physicians should be cognisant of the potential for extrapulmonary TB to develop.