Paraprotein-Negative IL-1-Mediated Inflammatory Dermatosis: An Update on Schnitzler-Like Syndrome in the Absence of a Gammopathy.

Schnitzler syndrome (SchS) is a rare autoinflammatory condition characterized by chronic urticaria and systemic inflammation. Obligate diagnostic criteria include the presence of a monoclonal IgM or IgG band, with nearly all cases demonstrating a prompt response to IL-1 blockade. Recently, "Schnitzler-like" cases without a paraprotein have been reported. Although the exact nature of their relation to the original eponymous syndrome remains unclear, these cases share similar clinical features and response to IL-1 inhibition. Diagnostic delay is common in autoinflammatory syndromes, and the need to recognize potentially emerging cases is important. We present the case of a male aged 47 years with refractory urticaria, joint pain, and systemic inflammation resembling SchS but without detectable paraprotein, consistent with recently proposed paraprotein-negative IL-1-mediated inflammatory dermatosis (PANID). After failing conventional therapies, the patient achieved rapid and sustained remission with IL-1 blockade. This case underscores the importance of recognizing autoinflammatory syndromes, including PANID, in patients with refractory urticaria with associated inflammatory features. It also highlights the importance of a therapeutic trial of IL-1 inhibition.