Selective JAK Inhibition in RA vs PV

Tofacitinib induced remission of rheumatoid arthritis but spared JAK2-driven polycythemia vera in a single case report.

By
Julia Cipriano
February 13, 2026
3 min

Conexiant

Overview

Tofacitinib demonstrated significant rheumatologic efficacy in a patient with seropositive rheumatoid arthritis and polycythemia vera, while having minimal impact on hematologic activity related to polycythemia vera. This case highlights the differential effects of JAK inhibitors across diseases driven by different JAK isoforms.

Background

The use of Janus kinase (JAK) inhibitors has become established in the treatment of autoimmune diseases like rheumatoid arthritis (RA). However, their effects can vary significantly depending on the underlying pathophysiology, particularly when JAK2 is involved, as seen in polycythemia vera (PV). Understanding these differences is crucial for optimizing treatment strategies in patients with overlapping autoimmune and myeloproliferative disorders.

Data Highlights

No numerical data available in the article.

Key Findings

Tofacitinib effectively induced remission of RA in a patient with concomitant PV.
Despite broad immunomodulatory effects, tofacitinib had limited impact on JAK2-driven erythrocytosis.
The patient achieved clinical and ultrasonographic remission of RA within 3 months of starting tofacitinib.
Hematologic parameters remained stable throughout the follow-up period.
After 12 months, the patient remained in RA remission without adverse events or cytopenias.

Clinical Implications

Clinicians should consider the differential effects of JAK inhibitors when treating patients with both autoimmune and myeloproliferative diseases. While tofacitinib can effectively manage RA symptoms, additional therapies targeting JAK2 may be necessary for optimal management of PV-related hematologic issues.

Conclusion

This case underscores the importance of understanding the specific actions of JAK inhibitors in different disease contexts. Further research is needed to explore the best therapeutic approaches for patients with overlapping conditions.