Description of a Large Family with Periodic Fever Carrying a Variant in RXFP1 Gene: A Possible Novel Modulator of Inflammation in Autoinflammatory Diseases

Autoinflammatory diseases involve recurrent systemic inflammation caused by dysregulated innate immunity, arising from genetic or multifactorial mechanisms, as seen in periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) syndrome. About 10% of PFAPA patients show autosomal dominant inheritance. We describe a three-generation family with a PFAPA-like recurrent fever syndrome displaying clear autosomal dominant transmission. All affected individuals tested negative on a diagnostic panel of 13 known autoinflammatory genes. Whole-exome sequencing was performed in two distantly related affected members, followed by variant filtering, segregation analysis, and phenotype-based prioritization. A single heterozygous missense variant in <i>RXFP1</i>, c.154G>A p.(Asp52Asn), co-segregated with disease in all affected relatives. This variant is extremely rare in population databases, absent from ClinVar, present in COSMIC, and predicted as damaging by REVEL and CADD. RXFP1, not previously implicated in autoinflammatory or innate immune disorders, encodes the relaxin family peptide receptor 1, a G protein-coupled receptor involved in extracellular matrix regulation, anti-fibrotic pathways, and modulation of inflammatory cytokine production. Protein network analysis showed interactions with RLXN1-3, inflammatory mediators, PTGDR, ADORA2B, and C1QTNF8, supporting an immunomodulatory function. This is the first report linking <i>RXFP1</i> variation to a hereditary recurrent fever syndrome, identifying relaxin signalling as a potential immune regulatory pathway.