RHUPUS SYNDROME: DESCRIPTION OF CLINICAL MANIFESTATIONS, ANALYTICAL FINDINGS, AND THERAPEUTIC APPROACH IN A SERIES OF 10 CASES

PV145a / #751 Poster Topic: AS17 - Miscellaneous Background/Purpose Rhupus is a rare syndrome that combines characteristics of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Its prevalence is estimated to be 0.09%. It is characterized by erosive polyarthritis along with typical SLE symptoms and specific autoantibodies. The debate continues as to whether Rhupus is a true overlap of RA and SLE or represents a form of SLE with erosive joint involvement. In order to provide a better understanding of the topic, the objective of this study is to describe the demographic variables, analytical data, clinical manifestations, and therapeutic approaches in patients diagnosed with Rhupus. Methods A cross-sectional, monocentric study was conducted on patients diagnosed with Rhupus between January 2019 and December 2024. All patients met the ACR/EULAR 2010 criteria for RA and ACR/EULAR 2019 criteria for SLE. Demographic variables, analytical data (autoantibodies, cytopenias, acute phase reactants, and complement consumption), clinical manifestations, and the different treatments received during their evolution, including synthetic and biologic DMARDs, were collected Results Ten patients were included, 90% women, with a median age of 62 years. All received treatment with at least 3 DMARDs. The most commonly used synthetic DMARDs were methotrexate and hydroxychloroquine. Seven patients received biologic DMARDs, with rituximab being the most commonly used. One patient was treated with certolizumab due to fertility desires. Six patients received JAK inhibitors (4 with baricitinib and 2 with upadacitinib) (Table 1). All patients tested positive for antinuclear antibodies (ANA), 90% for anti-citrullinated peptide (anti-CCP), 80% for rheumatoid factor (RF), and 60% for anti-double-stranded DNA (anti-dsDNA). Other antibodies present can be seen in Table 2. The most frequent analytical alterations were elevated acute phase reactants (100%), lymphopenia (40%), and complement consumption (30%). Regarding clinical manifestations, arthritis was present in 100% of patients, 70% of which was erosive. Fatigue and morning stiffness affected 60%. Thirty percent showed typical SLE skin lesions such as malar rash, photosensitivity, and subacute cutaneous lupus. Other manifestations, such as alopecia and dry syndrome, were present in 30%. Less frequently, aphthosis, rheumatoid nodules, pericarditis, pericardial effusion, pleural effusion, and Raynaud’s phenomenon were observed (Table 2). TABLE 1. DEMOGRAPHIC CHARACTERISTICS AND TREATMENTS TABLE 2. ANALYTICAL DATA AND CLINICAL MANIFESTATIONS Conclusions All patients presented with difficult-to-manage symptoms, requiring treatment with at least 3 DMARDs. The most frequently used treatments were methotrexate, hydroxychloroquine, JAK inhibitors (tofacitinib and upadacitinib), and rituximab. The most common analytical findings were elevated acute phase reactants, lymphopenia, and complement consumption. All patients had positive ANA, 90% had positive anti-CCP, 80% had RF, and 60% had anti-dsDNA. Arthritis was the most frequent manifestation (100% of patients), with 70% of cases being erosive. Other typical SLE manifestations were present, with the most frequent being skin lesions in 30% of patients.

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