Is the association between Immunoglobulin A Nephropathy and Spondyloarthritis real? A case-based review

Spondyloarthritis is a group of inflammatory rheumatic diseases characterized by inflammation of the spine and sacroiliac joints. Extra-musculoskeletal manifestations may also occur, although kidney involvement is rarely reported. Immunoglobulin A nephropathy is one of the most common types of glomerulonephritis, and it can be primary or associated with various diseases, such as SpA. Several cases have been reported, mostly through case reports and small case series, pointing to a possible common pathophysiology between these two diseases. However, there is scarce information on the prevalence of renal involvement, particularly Immunoglobulin A nephropathy, among Spondyloarthritis Portuguese patients. We present 5 cases of Immunoglobulin A nephropathy in patients with Spondyloarthritis, resulting from a multicentre Portuguese collaboration, accompanied by a systematic literature review to understand this possible association.