POS0332 PATTERNS AND DIFFERENCES IN ORGAN MANIFESTATIONS BETWEEN MICROSCOPIC POLYANGIITIS (MPA) AND GRANULOMATOSIS WITH POLYANGIITIS (GPA) IN A LARGE EUROPEAN COHORT
Authors: S. Krämer, T. Rauen, K. Vogt, T. Schreibing, M. Busch, R. Bergner, S. Mosberger, T. Schmitt, T. Neumann
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Multiple organ involvement is a typical feature of vasculitis in general, particularly in ANCA-associated vasculitis (AAV). The alignment of organ involvement to classification criteria has been previously confirmed [1]. <h3>Objectives:</h3> This study aimed to explore differences between GPA and MPA in terms of single organ involvement and especially overlaps in organ manifestations. <h3>Methods:</h3> We collected data from AAV patients at four tertiary referral centers (Germany and Switzerland) between 2000 and 2022, classification was performed in accordance with the 2022 ACR/EULAR criteria for GPA and MPA. Organ involvement was identified by BVAS entries. Important manifestation, regarding kidney, lung, ear, nose, and throat (ENT), and nervous system were compared between AAV-entities by Pearson's Chi<sup>2</sup>-test and their combinations illustrated graphically. <h3>Results:</h3> The dataset included 358 patients, of whom 168 (46.9%) were females, with a median age of 61 years (25-75 percentile: 50-70). According to the 2022 ACR/EULAR criteria, 203 (58.1%) were classified as GPA, 139 (38.8%) as MPA. Renal involvement was dominant in MPA (84.9%) compared to GPA (68.3%), while pulmonary affection was found in 59.6% in GPA vs. 38.8% in MPA. ENT involvement was present in 50% of all GPA cases but only in 11.5% of MPA cases, with all differences found to be significant (p &lt;.001). Isolated ENT involvement was completely uncommon in MPA (0%), whereas a combination with kidney and lung was documented in 8 cases, exclusively with kidney in 4, with lung in 4 cases, and a combination of nervous, renal, and pulmonary manifestations was documented once. Figure 1 visualizes the widespread distribution and most frequent combinations of organ manifestations in GPA in comparison to MPA. Of note, sole renal affection in MPA was found more frequently (39/139, 28.1%) than its combination with general symptoms (26, 18.7%) or overlapping with pulmonal manifestation (13, 9.4%). <h3>Conclusion:</h3> In our cohort, GPA exhibits a broader range of organ involvement compared to MPA, where a higher occurrence of single-organ manifestations is observed. The distinctions between GPA and MPA are evident in age, with notable differences in ENT involvement. In contrast to a previous German cohort study in 2016 [2], which reported 97.1% of MPA cases presenting with general symptoms, our current analysis indicates a significant number of cases displaying only kidney involvement without additional symptoms. This divergence may be attributed to the impact of the new ACR/EULAR criteria, leading to the classification of more cases as MPA with limited renal involvement. <h3>REFERENCES:</h3> [1] Krämer S, Rauen T, Vogt K, et a. Alignment Between the Novel 2022 ACR/EULAR Classification Criteria for ANCA-associated Vasculitis (AAV), Clinical Diagnosis and Organ Manifestations in a European AAV Cohort - ACR Meeting Abstracts. Arthritis rheumatol. (2023) 75 (supplement 9). [2] Schirmer HJ, Wright, NM, Vontheim R, et al. Clinical presentation and long-term outcome of 144 patients with microscopic polyangiitis in a monocentric German cohort. Rheumatology, Volume 55, Issue 1, January 2016, Pages 71–79. <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> Stefan Krämer: None declared, Thomas Rauen Vifor, Kristian Vogt: None declared, Theresa Schreibing: None declared, Martin Busch Vifor, Raoul Bergner Vifor, Sebastian Mosberger: None declared, Tobias Schmitt: None declared, Thomas Neumann Vifor.