AB0019 SYSTEMIC AUTOINFLAMMATORY DISEASE DIAGNOSES IN A SINGLE YEAR FROM A U.K. NATIONAL REFERRAL CENTRE
Authors: H. C. Caterson, H. J. Lachmann
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Systemic autoinflammatory diseases (SAIDs) are a group of inflammatory conditions whose diagnosis is frequently missed or delayed. The availability of genetic testing and the establishment of specialty clinics aims to increase awareness and diagnosis of these potentially treatable disorders. <h3>Objectives:</h3> To study the incidence and demographics of SAID diagnoses at a UK national referral centre and report our diagnostic experience. <h3>Methods:</h3> All new patients seen in the year 2022 in a UK national referral centre for primarily adult SAID were retrospectively reviewed. The medical records of the patients were reviewed up until November 2023 for demographics, comorbidities, phenotypes, genotypes, and pathology results. Genetic testing was either a next generation sequencing (NGS) panel of 25 SAID-related genes, or Sanger sequencing of individual genes. Patients were classified as having a SAID as per the decision of the clinic multidisciplinary meeting. <h3>Results:</h3> Patients: 306 new referrals were seen. 121 (39.5%) were male and 185 (60.5%) female. The ages at first review ranged from 3 to 94 years old. 270 (88%) were aged ≥18 years and 36 (12%) ≤17 years. 48% were Northern European, 21% West Asian/Jewish/Egyptian, 9% African descent, 5% mixed West Asian, 5% Southern European, and 5% South Asian. They were most commonly referred by rheumatology (47%), GP (17%), and dermatology (9). Diagnoses: 121 patients (39.5%) were diagnosed with a SAID and 185 (60.5%) did not have a SAID. The SAID group were 59% male and 41% female; 95 (79%) were new diagnoses and 26 (21%) were transition patients from paediatrics. 39 SAID patients (32%) were treated with biologic therapy. The spectrum of SAID diagnoses in the overall, new diagnoses, and transition patients are in Table 1. The most frequent diagnoses overall were familial Mediterranean fever (FMF) (31%), idiopathic recurrent pericarditis (IRP) (14%), and undifferentiated SAID (USAID) (11%). The mean age at diagnosis was 8 years (SD 5) for transition patients, 36 years (SD 17) for newly diagnosed adult or paediatric SAID, and 64 years (SD 10) for newly diagnosed late-onset/acquired SAIDs (VEXAS, Schnitzler's syndrome, or myelodysplastic syndrome-related USAID). The median diagnostic delay was 2 years (IQR 0 - 5.5) in transition SAID, 4.5 years (IQR 1 – 12.75) in new diagnoses, and 6 years (IQR 2 - 8.5) in late-onset SAID (Table 2). SAID patients had a mean of 3 previous misdiagnoses (SD 1.5), with infection the most common. Genetics: 302 patients (99%) had genetic testing. 59 SAID patients (49%) had results supportive of a monogenic disease. <h3>Conclusion:</h3> SAIDs are rare, however, our referral clinic had a clinically important incidence of diagnoses. Of 306 new patients, 39.5% were confirmed to have SAID. The most common diagnoses were FMF, IRP, and USAID. SAID diagnosis remains challenging and there were clinically significant diagnostic delays for all SAIDs. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>