Periodic Fever with Aphthous Stomatitis, Pharyngitis, and Cervical Adenitis Syndrome Is Associated with a CARD8 Variant Unable To Bind the NLRP3 Inflammasome

Abstract

Periodic fever with aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) is a relatively common autoinflammatory condition that primarily affects children. Although tendencies were reported for this syndrome, genetic variations influencing risk and disease progression are poorly understood. In this study, we performed next-generation sequencing for 82 unrelated PFAPA patients and identified a frameshift variant in the gene (CARD8-FS). Subsequently, we compared the frequency of CARD8-FS carriers in our PFAPA cohort (13.9%) with a healthy local population group (3.2%) and found a significant association between the CARD8-FS polymorphism and risk for PFAPA syndrome ( = 0.012; odds ratio: 4.96 [95% confidence interval, 1.33-18.47]). Moreover, CARD8-FS carriers display a distinct PFAPA phenotype that is characterized by a higher prevalence of symptoms out of flares and oral aphthosis (both = 0.02 compared with PFAPA patients without the frameshift variant). CARD8 encodes a protein component of the NLRP3 inflammasome, which plays an important role in inflammation and contributes to the pathology of various autoinflammatory diseases. We found that the CARD8-FS variant led to a truncated CARD8 protein lacking the FIIND and CARD domains. As a result, the mutant CARD8 protein lost the ability to interact with the NOD domain of NLRP3. In summary, these results identify a new CARD8 variant associated with PFAPA and further suggest that disruption of the interaction between CARD8 and NLRP3 can regulate autoinflammation in patients.

Loss-of-function CARD8 mutation causes NLRP3 inflammasome activation and Crohn’s disease

“…Studies of the proband's mother and maternal aunt also revealed high circulating levels of IL-1β and increased NLRP3 inflammasome activity, but in these cases, possible clinical responses to anti-IL-1β administration have not been tested. These data on the relation of a CARD8 mutation to causation of CD is parallel to a recent finding that a frameshift mutation in CARD8, also leading to reduced binding of CARD8 with NLRP3, is a cause of periodic fever with aphthous stomatitis, pharyngitis, and cervical adenitis (6).…”

“…Whole exome sequencing identified a number of variants in the patients who composed the above kindred (Supplemental Figure 1). Among these, the variant chr19:48741719 C>T (hg19) in CARD8 stood out because of its role in the inflammasome (5,6). This variant has an allele frequency of 0.0015% in the genome Aggregation Database (gnomAD; http://gnomad.broadinstitute.org/) (2 heterozygous individuals), is predicted to be possibly damaging/ deleterious by PolyPhen (http://genetics.bwh.harvard.edu/pph/ data/) and SIFT (http://sift.jcvi.org/), and has a CADD-PHRED score (http://cadd.gs.washington.edu/info) of 11.3, which is above In initial studies to examine this latter possibility, we determined concentrations of IL-1β and IL-6 in a random sample of proband serum by ELISA and found that concentrations of both of these cytokines were clearly increased compared with levels in sex-matched control sera ( Figure 2B).…”

“…In addition, these investigators showed that NLRP3 with mutations associated with cryopyrinassociated periodic syndromes (CAPS) increased inflammasome activity and lost the ability to bind to CARD8. Additional evidence of CARD8 inhibition of NLRP3 has come from studies by Cheung et al, who reported that a frameshift mutation in CARD8, resulting in loss of binding to NLRP3, caused a form of CAPS marked by aphthous stomatitis, pharyngitis, and cervical adenitis (periodic fever, aphthous stomatitis, pharyngitis, adenitis [PFAPA] syndrome) (6). These studies introduce the possibility that a loss-offunction mutation in CARD8 could be associated with increased NLRP3 inflammasome activity.…”

Risk factors for periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) syndrome: a case-control study

“…Previous studies reported an association between PFAPA symptoms and proinflammatory cytokine IL-1β production (4, 5). Cheung et al reported that a CARD8 polymorphism (CARD8-FS) in inflammasome-related genes was more common in PFAPA patients with a more severe phenotype (21). A TE, with removal of the microbial layer on the tonsils, in addition to lymphatic tissue, is a highly effective treatment for PFAPA syndrome (22).…”

The First International Conference on Periodic Fever, Aphthous Stomatitis, Pharyngitis, Adenitis Syndrome

“…[49][50][51][52][53] In an additional report, an association between PFAPA and a CARD8 variant that is unable to bind the NLRP3 inflammasome was found. 54 Decreased ability of CARD8 to bind NLRP3 is consistent with increased inflammasome activity and IL-1b production. Developing a better understanding of this overlay may further elucidate the precise mechanism through which the inflammasome influences PFAPA flares, ultimately leading to targeted therapeutic strategies.…”