Urolithiasis as an extraarticular manifestation of ankylosing spondylitis

Ankylosing spondylitis (AS) affects sacroiliac and axial joints as well as extraarticular organs, such as the eye, lung, bowel, and heart. Although examples of renal involvement in AS, such as IgA nephropathy, amyloidosis, and glomerulonephritis, have been reported, it has not been emphasized that urolithiasis is frequently formed in the clinical course of AS. Growing evidence indicates that urolithiasis may be observed in AS patients and is more frequent than other extraarticular features. In this review, we will discuss frequency and predictors of AS-related urolithiasis and summarize the possible underlying genetic and biochemical mechanisms. We believe an increased awareness of urolithiasis as a complication of AS will encourage future studies that will shed light on disease mechanisms and preventative therapies.