Selective JAK Inhibition in RA vs PV - Takeaways - MDSpire

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

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  • 1

    Tofacitinib demonstrated rheumatologic efficacy in a patient with rheumatoid arthritis and polycythemia vera, but had minimal effect on hematologic activity.

  • 2

    JAK inhibitors primarily target JAK1 and JAK3, sparing JAK2, which is crucial in polycythemia vera pathogenesis.

  • 3

    The patient achieved clinical and ultrasonographic remission of rheumatoid arthritis within three months of starting tofacitinib.

  • 4

    Hematologic parameters remained stable during tofacitinib treatment, allowing for a reduction in hydroxyurea dosing.

  • 5

    Tofacitinib's limited effect on erythrocytosis highlights the need for JAK2-directed therapies in patients with autoimmune and myeloproliferative diseases.

Original Source(s)

Selective JAK Inhibition in RA vs PV

  • by Julia Cipriano

  • February 13, 2026

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