Undifferentiated spondyloarthritis is a disease that has clinical and radiological features that support spondyloarthritis but does not have any of the diagnostic criteria that have now been established for spondyloarthritis. Undifferentiated spondyloarthropathy may be an early stage of a spondyloarthropathy that will later develop into a classic spondyloarthropathy, an overlapping syndrome, or a spondyloarthropathy that can be clearly classified in the future but cannot be defined at this time. Undifferentiated spondyloarthritis is more common in young men and is characterized by asymmetric arthritis, tendon terminal inflammation, sacroiliac arthritis, and other inflammatory mesial joint involvement, as well as characteristic systemic manifestations such as iritis and conjunctivitis.