Some patients present with overlapping clinical manifestations of spondyloarthropathies, but cannot be diagnosed with a specific spondyloarthropathy. These patients may be early stage patients with ankylosing spondylitis, or may develop typical ankylosing spondylitis in the future, or may have an “aborted” form of ankylosing spondylitis (which does not develop into typical ankylosing spondylitis), or a lifetime of overlapping manifestations that cannot be identified as either type of seronegative spondyloarthropathy. 2. Undifferentiated spondyloarthropathy is diagnosed when a patient with a suggested spondyloarthropathy does not meet the diagnostic criteria for ankylosing spondylitis and other definite spondyloarthropathies such as Reiter’s syndrome, psoriatic arthritis, and enteropathic arthritis can be excluded.