Vascularite urticarienne associée à une thrombocytémie essentielle avec myélofibrose secondaire Urticarial vasculitis associated with essential thrombocythaemia progressing to myelofibrosis

Summary Background. — Urticarial vasculitis(UV) is a rare form of leukocytoclastic in whichskin lesions resemble urticaria. UV comprises hypocomplementemic and normocomplemente-mic subtypes. To date, only 4 cases of UV associated with myeloproliferative disorders havebeen described, including 3 cases withessential thrombocythaemia (ET) and one casepolycythaemia vera. Patients and methods.— We describe the case of a 59-year-old male patient with JAK2-positiveTE and secondary myelofibrosis and who developed multiple urticarial papules persisting formore than 24hours. Skin biopsy showed perivascular neutrophilic infiltrate with marginationof neutrophils in the lumen of vessels and some leukocytoclastic patterns, and with red cellextravasation consistentwithUV.Treatmentwithruxolitinib(aJAK2inhibitor)inducedtransientand partial control of the haematological symptoms but did not prevent UV flare. Prednisolone20 mg once daily was added, with good clinical response. Discussion and conclusion.— To our knowledge, this is the fourth reported case of UV associatedwith