Patients with clinical or imaging signs of inflammation at the sacroiliac or spinal joints without other signs making it possible to establish one of the above-mentioned rheumatic diagnoses are usually grouped under the term undifferentiated spondyloarthritis. This group encompasses only non-radiograph axSpA as the presence of radiographic changes fulfilling the criteria for AS imply the presence of this diagnosis. During the course psoriasis, inflammatory bowel disease or radiographic sacroiliitis may supervene and contribute to a classification in one of the well-defined forms of axSpA.