SAT0533 ADULT ONSET STILLS DISEASE AND IDIOPATHIC RECURRENT PERICARDITIS: ARE THE MORE SIMILARITIES OR DIFFERENCES?
Authors: V. Myachikova, O. Moiseeva, E. Kuvardin, S. Lapin, O. Tkachenko, V. Nazarov, A. Maslyanskiy
Journal: Annals of the Rheumatic Diseases (2020)

Background: Adult onset Stills disease (AOSD) and Idiopathic recurrent pericarditis (IRP) are currently considered auto-inflammatory diseases. Common features of these disorders are symptoms such as fever, leukocytosis, serositis, increased acute phase reactants. Diagnosis of IRP is based on ESC 2015 diagnostic criteria, while AOSD is defined according to 3 sets of classification criteria. A detailed study shows that modern criteria for these nosologies overlap and do not allow distinguishing one from the other. Objectives: We have not found any data on the comparison of the two groups in the literature. We compared the two groups of patients according to several parameters, such as clinical features, laboratory testing, genetic analysis to identify common patterns. Methods: We enrolled 22 newly identified subjects (13 patients with AOSD, 9 patients with IRP) to our prospective, monocenter study. The mean age of patients with AOSD was 31 [22; 39], the mean age of patients with IRP was 46 [35;54]. Blood sampling in all patients was performed in the flare. We quantified the serum levels of ferritin and its glycosylated fraction in both groups. Mutations of the MEFV, TNFRSF1A genes were studied. As more sensitive imaging methods for lymphadenopathy and serositis, we performed the following instrumental studies for all patients: transthoracic echocardiography, ultrasound of the abdominal cavity and pelvis, chest high-resolution computed tomography. Results: One subject with a heterozygous missense variant was found in exon 2 of the MEFV gene (E148Q) in the IRP group. The patient was excluded from our study. Elevated white blood cell (WBC) count and C-reactive protein (CRP) were observed in all patients in 2 groups, however, the level of WBC greater than 10,000/mm 3 was found only in 10 patients from the AOSD group and 5 – from the IRP. Elevated ferritin level in both groups was detected. The number of subjects with high level of ferritin in the AOSD group reached 12 (n=13), in the IRP group – 7 (n=8). The ferritin level appeared to be more significant in the AOSD group compared to the IRP group (1521 ng/ml vs 408 ng/ml p=0.0159) Figure 1.In turn, lower glycosylated ferritin was recorded in 9 patients with AOSD (n=13), and 7 – with IRP (n=8). We have demonstrated a more significant decrease of glycosylated ferritin level in patients with AOSD in comparison to patients with IRP, which amounted (11% vs 37% p = 0.0286) reference value (38.6%-84.7%). Figure 1. Abnormal liver function tests were found in the majority of patients with AOSD and IRP (61% vs 75%). We have also shown that, if the patient had pericardial effusion, the fluid was present in the pleural cavity, regardless of the group. The number of AOSD patients with polyserositis was 5 (n=13). Other symptoms are presented in Table 1 Table 1 Symptom and sign AOSD (n=13) IRP (n=8) CRP mg/L, mean, % 123 [69;164], 100% 151[65; 226], 100% Pericarditis 38% 100% Pleuritis 38% 100% Leukocytosis ≥10,000/mm3 77% 62% Abnormal liver function tests 61% 75% Fever &gt;39 °C 100% 100% Rush 77% 0 % Arthralgia 100% 75% Arthritis, lasting 2 weeks or longer 100% 12.5% Sore throat 54% 0% Recent lymphadenopathy 85% 25% Hepatomegaly or splenomegaly 54% 62% Elevated ferritin 92% 87% Glycosylated ferritin ≤20% 69% 25% Conclusion: The level of ferritin in the IRP group was lower, which can be explained by a less generalized process, the absence of such symptoms as arthritis, rash, splenomegaly. Diagnostic and classification criteria of both disorders do not allow distinguishing between the diseases. There might be no differences between the diseases; further research (on more representative groups) is needed. We consider the comparison of the gene-expression analysis in these patients to be of great importance. Disclosure of Interests: None declared