Background: Janus Kinases (JAK) can promote cytokine production in immune and hematopoietic cells. The JAK-2 (V617F) mutation is the most frequently detected mutation in myeloproliferative neoplasms (MPN) which include essential thrombocythemia (ET), polycythemia vera (PV), primary myelofibrosis (PMF) and undifferenciated MPN. JAK-2 (V617F) mutation displays a pro-inflammatory phenotype that may be associated to a higher risk of immune mediated diseases (IMID).

Objectives: In a wide series of JAK2 (V617F) mutation, we assess the presence of a) IMID (rheumatic and non-rheumatic), b) treatment of rheumatic IMID.

Methods: We studied all the patients diagnosed with a positive JAK-2 (V16F) mutation in a single University Hospital from January 2004 to December 2019. JAK-2 (V16F) mutation was detected by using both peripheral blood and bone marrow samples. Associated IMID and treatment of rheumatic IMID were evaluated.

Results: We included 130 patients (73 men/57 women; mean age, 70.1±14.5 years). All of them were diagnosed of MPN; ET (n=64, 49.2%), PV 46 (35.4%), undifferentiated MPN (n=12, 9.2%) and PMF (n=8, 6.1%). In 10 of these 130 patients (7.7%) a rheumatic IMID was diagnosed: rheumatoid arthritis (RA) (n=4; 40%), polymyalgia rheumatica (PMR) (n=3; 30%), Sjögren syndrome (SS) (n=1; 10%), antiphospholipid syndrome (APS) (n=1; 10%) and autoinflammatory syndrome (WDR1 mutation) (n=1; 10%). Patients with RA, SS, PmR, and APS were clinically mild. RA patients were seronegative, non-erosive and without extraarticular involvement. Treatment and response are summarized in Table 1 . All patients diagnosed with PMR were treated with glucocorticoids (prednisone 5 mg/12 hours), SS with hydroxychloroquine (HCQ) (200 mg/day), APS was anticoagulated with acenocumarol and one autoinflammatory syndrome was finally treated with baritinib (4 mg/day) after failure to anakinra (100 mg/day).

Conclusion: Except in autoinflammatory syndrome, most rheumatic IMID associated to JAK-2 (V16F) mutation are clinically mild, and treatment and response of patients seems similar or even better than those without this mutation.

Table 1.

Treatment of 10 patients with rheumatic IMIDs and JAK-2 (V16F) mutation.

Abbreviation: ANA: anakinra, BARI: baricitinib, NSAIDs: Non-Steroidal Anti-inflammatory Drugs, PDN: prdnisone, RA: Rheumatoid arthritis, SS: Sjögren syndrome, PMR: polymyalgia rheumatica.

Disclosure of Interests: Carmen Álvarez-Reguera: None declared, Lara Sanchez-Bilbao: None declared, Sara Fernández López: None declared, Ana Batlle-López: None declared, Alba Herrero-Morant: None declared, David Martínez-López: None declared, Miguel Á. González-Gay Speakers bureau: Abbvie, Pfizer, Roche, Bristol-Myers, Janssen, Lilly and MSD, Grant/research support from: Abbvie, Pfizer, Roche, Sanofi and MSD., Ricardo Blanco Speakers bureau: Abbvie, Pfizer, Roche, Bristol-Myers, Janssen, Lilly and MSD., Grant/research support from: Abbvie, MSD and Roche.