Schnitzler syndrome co-occurring with idiopathic multicentric Castleman disease that responds to anti-IL-1 therapy: A case report and clue to pathophysiology.

Patients with HHV-8-negative/idiopathic multicentric Castleman disease (iMCD) experience systemic inflammatory symptoms and polyclonal lymphoproliferation due to an unknown etiology. Schnitzler's syndrome (SS) is characterized by recurrent urticarial rash, monoclonal IgM gammopathy, and other clinical signs of inflammation. To our knowledge, we report the first case of iMCD associated with SS and the fourth case of anakinra inducing a complete response for an iMCD patient. A forty-four year old woman with a history of a recurrent urticarial rash, presented to our hospital complaining of 6 months of night sweats, fever, chronic urticaria, iliac bone pain, and generalized lymphadenopathy. An IgM Kappa monoclonal component was measured at 7.8g/L. A lymph node biopsy revealed histopathological features consistent with the plasma cell variant of iMCD. She was diagnosed with SS and iMCD. Anti-IL-1 treatment with anakinra (100mg/day) was introduced. Within 48h, we observed improvement in the fever and the urticarial rash. By one month, we considered the patient in complete remission. Two years later, the remission is persistent while the patient is still under therapy. Though this is only the fourth reported case of anakinra in iMCD, this is yet another case demonstrating the effectiveness of anti-IL-1 blockade in SS. We hypothesize that uncontrolled cytokine production is responsible for both the SS and the iMCD. The etiologies of SS and iMCD are unknown, and future research is necessary.