Schnitzler syndrome - a rare cause of chronic urticaria. Case report.

Schnitzler syndrome (SchS) is a very rare acquired systemic disease that has many similarities to hereditary autoinflammatory syndromes. The condition is characterized by the presence of monoclonal gammopathy and chronic urticaria. In this case report, a 64-year-old male patient with SchS was initially misdiagnosed with chronic spontaneous urticaria (CSU). The patient was treated with anakinra, showing good tolerance and no need for steroid therapy for 14 months. SchS is often underdiagnosed and presents symptoms such as prolonged urticarial wheals and systemic manifestations. The differential diagnoses include mastocytosis, urticarial vasculitis, and autoimmune diseases. The diagnostic criteria were elevated CRP levels, neutrophilic skin infiltration, leukocytosis, and abnormal bone remodeling on scintigraphy. Treatment options include highly effective interleukin-1 blockade therapies such as anakinra, canakinumab, and rilonacept. This case emphasizes the importance of a thorough differential diagnosis of chronic urticaria and encourages clinicians to participate in the SchS database for improved recognition and management.