New-Onset Raynaud Phenomenon during Ropeginterferon Alfa-2b Therapy for Polycythemia Vera: A Case Report and Review of the Literature.

Introduction: Ropeginterferon alfa-2b is increasingly used as a disease-modifying cytoreductive therapy for polycythemia vera (PV), achieving durable hematologic control and molecular responses. Raynaud phenomenon may occur in myeloproliferative neoplasms and is listed as an uncommon adverse reaction to ropeginterferon alfa-2b. However, detailed published reports of Raynaud phenomenon occurring during ropeginterferon alfa-2b therapy remain scarce. Case Presentation: A patient with JAK2 V617F-positive PV initiated ropeginterferon alfa-2b due to inadequate hematocrit and platelet control. Blood counts normalized and the JAK2 V617F variant allele burden declined. During therapy, the patient developed cold-triggered, sharply demarcated digital pallor followed by painful cyanosis which resolved with rewarming, consistent with Raynaud phenomenon. Autoimmune and vascular evaluations were unremarkable, and the Raynaud phenomenon was considered treatment related. Conclusion: New-onset Raynaud phenomenon during ropeginterferon alfa-2b therapy may represent a rare treatment-related vascular adverse effect. With the growing use of interferon-based therapies, clinicians should routinely monitor for vasospastic symptoms and carefully distinguish these from disease-related microvascular manifestations.