Syndrome of undifferentiated recurrent fever (SURF): a multicenter real-world experience from Türkiye.

Introduction/objectives: Syndrome of undifferentiated recurrent fever (SURF) is an autoinflammatory disorder that is recognised in an increasing number of patients. In this study, we aimed to assess the data of SURF patients from the main reference centres in our country.

Methods: Data for this retrospective multicentre observational cohort study were obtained from the records of SURF patients aged 0-18 years who were followed up in 10 pediatric rheumatology clinics in Türkiye between 2010 and June 2023. Patients with recurrent fever that could not be explained by periodic fever, aphthous stomatitis, pharyngitis and adenopathy (PFAPA) and hereditary recurrent fevers and had no other cause were included in the study.

Results: Of the 134 patients included in the study, 74 (55.2%) were male. The median age at diagnosis was 67 months. The most common symptom was abdominal pain in 98 (73.1%), arthralgia in 82 (61.2%), malaise in 77 (57.5%). The age at symptom onset was ≤ 5 years in 109 patients (81.3%). Pharyngitis was more common symptom in children aged ≤ 5 years (p = 0.008), headache, arthralgia, chest pain were more common findings in children > 5 years (p = 0.008, p = 0.032, p = 0.045). There were 113 patients receiving colchicine alone or in combination therapy and 74.3% of them achieved complete or partial remission. The presence of abdominal pain (p = 0.021, OR = 0.254) increased the remission rate with colchicine.

Conclusion: SURF patients present with a wide range of clinical manifestations. Distinguishing between SURF and PFAPA is not concrete. Further omics studies will enlighten whether there is a true group of SURF. Key Points • SURF is an autoinflammatory disease that is becoming increasingly recognised. • The clinical manifestations of SURF are quite heterogeneous. • Colchicine and anti-IL-1 treatment is effective in most SURF patients. • It is controversial whether it should be called SURF or PFAPA-like syndrome, especially in children aged ≤ 5 years.