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Normal Counts, High Risk: Abdul Mannan Breaks Down JAK2 + Splanchnic Vein Thrombosis
Dr Abdul Mannan/LinkedIn
Dec 12, 2025, 22:27

Normal Counts, High Risk: Abdul Mannan Breaks Down JAK2 + Splanchnic Vein Thrombosis

Abdul Mannan, Consultant Haematologist at Betsi Cadwaladr University Health Board, posted on LinkedIn:

”You find JAK2V617F in a patient with splanchnic vein thrombosis. Counts are normal. The marrow doesn’t show MPN. Now what?

Here’s the thing: JAK2 positivity in SVT means clonal, persistent risk. It doesn’t disappear just because the blood count looks normal.

Here’s what the evidence tells us:
• JAK2+ SVT behaves as a chronic prothrombotic state, even without overt MPN on counts or marrow
• Budd-Chiari syndrome should get indefinite anticoagulation from the start (target INR 2-3 with LMWH or VKA )
• Portal or mesenteric vein thrombosis with JAK2 positivity usually needs extended or indefinite anticoagulation, tailored to bleeding risk
• Ruxolitinib (Jakavi) is NOT standard for thrombosis prevention alone – it may help if an overt MPN later declares itself, but it doesn’t replace anticoagulation
• Cytoreduction isn’t indicated when counts are truly normal

Here’s what matters for follow-up: some patients do progress to overt MPN over time. One cohort had 30% declare MPN at a median of 41 months. So you’re looking at periodic CBCs, iron studies if polycythemia concerns you, and keeping step with hepatology for varices and bleeding risk.

The lesson for clinic: don’t withhold anticoagulation waiting for “diagnostic” marrow features, and don’t reach for ruxolitinib to avoid anticoagulation. Both are misses.

What’s your approach when JAK2 shows up in unusual thrombosis?”

JAK2

Keep up with Hemostasis Today.

Abdul Mannan Anticoagulation Betsi Cadwaladr University Health Board Budd-Chiari Syndrome Health Hematology Hemostasis Hemostasis Today JAK2 Mutation JAK2V617F Medicine MPN Myeloproliferative Disorders myeloproliferative neoplasms ruxolitinib Splanchnic Vein Thrombosis SVT thrombosis
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