In-vitro NLRP3 functional test assists the diagnosis of cryopyrin-associated periodic syndrome (CAPS) patients: A Brazilian cooperation

To report our five-years experience on the use of NLRP3 inflammasome functional assays in the differential diagnosis of Brazilian patients with a clinical suspicion of CAPS.The study included 9 patients belonging to 2 families (I, II) and 7 unrelated patients with a clinical suspicion of AID according to Eurofever/PRINTO classification, recruited between 2017 and 2022. The control group for the NLRP3 functional assay consisted of 10 healthy donors and for the CBA cytokines measurement of 19 healthy controls. Patients underwent clinical evaluation, genetic and functional analysis.All members of the family I received the diagnosis of Muckle-Wells Syndrome (MWS), carried the NLRP3 Thr348Met variant and resulted positive for the functional assay. The 2 patients of the family II resulted negative for the mutational screening but positive for the functional assay compatible with a MWS clinical phenotype. In 2 unrelated patients with NLRP3 mutations, including a novel mutation (Gly309Val, Asp303His), a positive functional test confirmed the clinical diagnosis of NOMID. 3 unrelated MWS and 1 FCAS patients resulted negative to the genetic screening and positive for the functional test. One patient with a FCAS-like phenotype harbored the NLRP12 His304Tyr variant confirming the diagnosis of FCAS2.The NLRP3 inflammasome functional assay can assist the clinical diagnosis of CAPS even in patients with unknown genetic defects.