JAK Inhibitor Clinical Response in Polyarthritis: Case Report

The heterogeneity of rheumatoid arthritis (RA) presentation and molecular signature of RA subclasses in patients with early changes of small peripheral joints still remains a challenging problem. In clinical setting, classification of the disease subtypes is not possible and treatment adjustment is based on the continuous Disease Activity Score for disease severity recognition. A new approach in the treatment appears with the novel non biologic targeted synthetic disease-modifying antirheumatic drugs from the group of Janus kinase 1 and 3 (JAK1 and JAK3), blocking interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15 and IL-21. We report a case of a 48-year-old patient who had suffered from polyarthritis from his age 40. Initial laboratory tests showed low inflammatory parameters and magnetic resonance imaging of both hands indicated an early stage of RA. Methylprednisolone and methotrexate therapy was initiated. The patient underwent additional tests, but there was not sufficient evidence for a precise diagnosis. According to the European League Against Rheumatism/American College of Rheumatology score-based algorithm, the patient was classified as seronegative RA based on joint involvement, duration of the disease, and synovitis not better explained by another disease. A partial clinical effect of the administered therapy (steroids as monotherapy and in combination, methotrexate and leflunomide) was noticed with the use of systemic steroids, but dramatic improvement was only achieved with a JAK inhibitor targeted therapy. Although the use of anti TNF-α blocker is a proposed procedure and the drug has not yet been registered in Europe, we took the opportunity to apply this new medication option. The patient, a construction worker, was treated for 20 months, which led to complete remission of the disease, without the need of basic or corticosteroid therapy. Full functional capacity necessary in his demanding job was also achieved. This result raised a question of timely introduction of immunomodulators in the polyarthritis treatment steps