RNF213-associated urticarial lesions with hypercytokinemia

Background Urticarial lesions are observed in both cutaneous and systemic disorders. Familial forms of urticarial syndromes are rare and can be encountered in systemic autoinflammatory diseases. Objective We sought to investigate a large family with dominantly inherited chronic urticarial lesions associated with hypercytokinemia. Methods We performed a genetic linkage analysis in 14 patients from a 5-generation family, as well as whole-exome sequencing, cytokine profiling, and transcriptomic analyses on samples from 2 patients. The identified candidate protein was studied after in vitro expression of the corresponding normal and mutated recombinant proteins. An unsupervised proteomic approach was used to unveil the associated protein network. Results The disease phenotype of the most affected family members is characterized by chronic urticarial flares associated with extremely high plasma levels of proinflammatory (IL-1β, IL-6, and TNF-α) and anti-inflammatory (IL-10 and IL-1 receptor antagonist [IL-1RA]) cytokines, with no secondary organ dysfunction, no susceptibility to infections, no fever, and normal C-reactive protein levels. Monocyte transcriptomic analyses identified an immunotolerant profile in the most affected patient. The affected family members carried a loss-of-function mutation in RNF213 that encodes mysterin, a protein with a poorly known physiologic role. We identified the deubiquitinase CYLD, a major regulator of inflammation, as an RNF213 partner and showed that CYLD expression is inhibited by wild-type but not mutant RNF213. Conclusion We identified a new entity characterized by chronic urticarial lesions associated with a clinically blunted hypercytokinemia. This disease, which is due to loss of function of RNF213, reveals mysterin’s key role in the complex molecular network of innate immunity.