Ruxolitinib-responsive histiocytoid sweet syndrome in a patient with polycythemia vera in hematologic remission – a case report

Abstract To describe the treatment response of histiocytoid Sweet syndrome (SS) refractory to colchicine and dapsone in a patient with high-risk polycythemia vera (PV) despite hematological complete remission (CR), following treatment with the JAK 1/2 inhibitor ruxolitinib. We report the case of a 78-year-old man with high-risk PV who achieved hematological CR with hydroxyurea. More than five years later, he developed a histiocytoid SS, and treatment with corticosteroids (CS) resulted in temporary complete resolution of SS. At the first relapse, SS recurred promptly when the CS dose was tapered below 10 mg daily. The malignancy-associated histiocytoid SS was refractory to colchicine or dapsone. Given the potent anti-inflammatory and immunosuppressive properties of ruxolitinib and its established role in the treatment of PV, therapy was switched to ruxolitinib in an attempt to treat both PV and SS. This approach resulted in complete resolution of histiocytoid SS within six weeks of initiating ruxolitinib, with sustained remission after discontinuation of CS, while remission of PV was maintained. In secondary (reactive) SS, treatment of the underlying disease is a mainstay of therapy. In patients with hematological malignancies and associated SS, modification of the underlying disease treatment may be considered even in the presence of hematological CR, particularly when conventional SS therapies fail. Close collaboration between hematologists and dermatologists is essential.