Background. Gain-of-function mutations of the NLR family pyrin domain containing 3 (NLRP3) gene have been implicated in autoinflammatory diseases. The NLRP3 Q703K variant is a common variant associated with Cryopyrin-associated periodic syndromes (CAPS) and periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA) syndrome. However, the genotype-phenotype correlation between NLRP3 Q703K variant, CAPS and PFAPA is unclear. In this study, we aimed to investigate the frequency of the NLRP3 Q703K variant in patients with and without autoinflammatory disease and characterize the phenotype in only Q703K variant positive patients.

Methods. A retrospective analysis of 639 patients with autoinflammatory symptoms was conducted. Patients underwent next-generation sequencing (NGS) panel analysis of 16 genes, including NLRP3. For the 68 patients carrying the only Q703K variant, their clinical and demographic information was evaluated. Genetic data from 1461 patients without autoinflammatory symptoms were used as the control group.

Results. Of our 639 autoinflammatory symptomatic patients, the Q703K mutation was detected in 68 (5.3% allele frequency). Heterozygous mutations were detected in 141 patients without autoinflammatory symptoms (4.8% allele frequency, p=0.4887). Of the patients with variant in Q703K, 10 patients were diagnosed with CAPS , 7 patients were diagnosed with PFAPA and the remaining 39 were diagnosed with undefined systemic autoinflammatory disease (uSAID) Conclusions. The Q703K variant, which is seen with similar frequency in the control and autoinflammatory groups, is also of higher prevalence in patients with mild CAPS symptoms and PFAPA syndrome. This variant, together with other undetected genetic variants or epigenetic modifications, may be responsible for the corresponding phenotype. As such, it is essential for clinicians to evaluate their patients using both genetic and clinical evaluations.

Keywords: aphthous stomatitis, cryopyrin-associated periodic syndromes; periodic fever, pharyngitis and cervical adenitis; NLRP3 gene; Q703K variant