Examining the clinical and radiological landscape of rhupus: navigating the challenges in disease classification

Rhupus, in the broad sense, refers to an overlap between rheumatoid arthritis (RA) and lupus. However, there is a paucity of data on the appropriate diagnostic/classification criteria that should be used to define rhupus. Hence, we undertook this narrative review to analyze the clinical characteristics, radiology, and treatment with a focus on diagnostic challenges and defining features of rhupus. The databases of Medline/PubMed, Scopus, and DOAJ were searched for relevant articles using the following keywords: ("Rhupus"), ("lupus" AND "erosive" AND "arthritis"), and ("lupus" AND "rheumatoid arthritis" AND "overlap"). Studies have used a variety of classification criteria for rhupus of which a combination of the latest classification criteria for RA and lupus along with positive anti-cyclic citrullinated peptide, anti-Smith, and anti-dsDNA antibodies seem most relevant. The majority of rhupus cohorts report the onset of the disease as RA (two-thirds of rhupus patients) followed by the development of features of lupus at an average interval of 3-11.3 years. The radiographic features and distribution of erosions are similar to RA. However, ultrasonography and MRI reveal erosions in pure lupus related arthritis as well. This makes the reliability of radiologic tools for the evaluation of rhupus supportive at the most. Extra-articular features in rhupus are mild with major organ involvement in the form of neuropsychiatric lupus and lupus nephritis being rare. We have further discussed the fallacies of the various classification criteria and proposed a theme for classifying rhupus which needs to be tested and validated in future studies. Our current state of understanding supports rhupus as an overlap of SLE and RA with articular disease similar to RA with the extra-articular disease being milder than SLE. Developing standardized classification criteria for rhupus will help in the early diagnosis and prevention of articular damage in patients with rhupus.