Individuals with PFAPA heterozygous for mutations in the MEFV (FMF), NLRP3 (CAPS), MVK (MKD/HIDS), TNFRSF1A (TNF-receptor associated periodic syndrome -TRAPS), and CARD15/NOD2 (Blau syndrome) genes often exhibit atypical symptoms like abdominal pain and arthralgias. This evidence concerns the gene MEFV and mevalonic aciduria.