Ab0039 Clinical Realities in Patients With Adult Onset Still’s Disease: Adapting to Patients Outside Conventional Criteria

Background: Adult Onset Still's Disease (AOSD) is a rare systemic inflammatory disorder characterized by inflammatory polyarthritis, daily fever, and a transient salmon-pink maculopapular rash. The diagnosis of AOSD is challenging as patients may have a variety of non-specific symptoms and laboratory abnormalities, and diagnosis of the disease is often exclusionary due to the ambiguous nature of its presenting symptoms. Objectives: To describe a cohort of AOSD patients and their fulfillment of various AOSD diagnostic criteria as seen in outpatient clinic visits at a tertiary care referral hospital in the United States. Methods: We enrolled in adult patients (≥18 years) with AOSD in a prospective cohort. Patients were first identified by ICD-10 codes (M06.1). Clinical diagnosis of AOSD was then confirmed with the patients' respective treating rheumatologists, and subsequently via chart review by a second rheumatologist who oversees a specialized AOSD practice. Patients with a different autoimmune/autoinflammatory disease that explained the clinical picture better than AOSD were excluded, and patients were then enrolled in the cohort. Demographic data, medication use, medical history, and laboratory results were collected via chart review. Patients were also characterized using three standard diagnostic criteria for AOSD –Yamaguchi, Cush, and Fautrel – and descriptive statistics were reported. Results: 33 patients were enrolled in the study, majority White (63.6%) and female (72.7%) (Table 1). Of the three examined diagnostic criteria, 69.7% of patients met Yamaguchi criteria, 36.4% met Cush criteria, and 45.5% met Fautrel criteria. Only 30.3% of patients met all of the examined diagnostic criteria, and 24.2% of patients fit none of the examined diagnostic criteria (Figure 1). All patients were treated clinically as AOSD despite differences in fulfilling AOSD diagnostic criteria. Treatment most commonly involved glucocorticoids (93.9%) and biological disease-modifying anti-rheumatic drugs (DMARDs) (81.8%), of which anakinra was most frequently utilized biologic DMARD (66.7%) and methotrexate was the most commonly utilized conventional DMARD (54.5%) (Table 1). 21.2% of patients had a history of macrophage activation syndrome (MAS). Patients with history of MAS were younger (mean 29.0 years, SD 11.1) than patients without (mean 42.4 years, SD 13.1). Hematologic involvement was identified in 29 total patients (87.9%), and cardiac involvement in 11 (33.3%). Peak ferritin levels were markedly elevated in the cohort (median 1800.5 ng/mL, IQR 483, 11390.5, n=32). 11 patients presented with elevated peak ferritin levels >10,000 ng/mL, including 6 with history of MAS. Conclusion: We characterized a cohort of patients who were treated clinically as AOSD and identified that 24.4% did not fit diagnostic criteria. Further, only 10 patients (30.3%) met all three criteria. It is imperative to recognize that not all patients neatly fit into established criteria, and there are patients who can be excluded depending on which criteria was selected, highlighting the heterogeneity of the disease. In most clinical trials, exclusion of patients who do not meet a particular AOSD criteria can be a challenge as it may lead to a potential underrepresentation of diverse patient populations in a heterogenous disease. Continued characterization of the disease is necessary in rare diseases where traditional diagnostic criteria may not be the clinical reality. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: Chloe Heiting: None declared, Karen Gambina: None declared, Bella Mehta Janssen Pharmaceuticals - Advisory Board Novartis – Honoraria.