Simultaneous occurrence of ankylosing spondylitis and diffuse idiopathic skeletal hyperostosis: a systematic review.

Objectives: AS and DISH are both spinal ankylosing conditions with a 4-fold increased risk of spinal fractures. The most commonly used criteria for DISH were designed to exclude radiographic signs of spondyloarthritis. However, case reports describing the presence of both conditions exist. In this study, the co-occurrence of AS and DISH were reviewed in the literature to explore the potential need to revise the criteria for DISH. Methods: A search was conducted in Pubmed, Embase, Web of Science and the Cochrane library using the terms 'spondyloarthritis' and 'DISH' and their matching synonyms. Full-text articles describing the coexistence of both conditions in the same patient were included. A quality assessment was performed, and the case descriptions were extracted. Results: Twenty articles describing simultaneous occurrence of AS and DISH in 39 cases were retrieved. All articles were case reports or series of moderate quality. Back or neck pain was present in 97% of the patients (mean age 61.2 years, 90% male) and HLA-B27 was positive in 9/27 documented measurements. Radiographic abnormalities were described in the SI joint (82% AS, 13% DISH) and in the spine (49% AS, 100% DISH). Conclusion: Simultaneous occurrence of AS and DISH has been reported in the literature in at least 39 cases. AS and DISH should not be seen as mutually exclusive. If the results of the current study are confirmed in a large observational study, revision of the current criteria to include the co-existence of both conditions should be considered.