Which antigen is associated with the diagnosis of Ankylosing spondylitis?

The antigen associated with the diagnosis of Ankylosing spondylitis is HLA-B27. This antigen is a specific human leukocyte antigen (HLA) that is part of the major histocompatibility complex (MHC) class I molecules. The presence of HLA-B27 is strongly linked to an increased risk of developing Ankylosing spondylitis, an inflammatory arthritis that primarily affects the spine and can lead to fusion of the vertebrae.

Studies have shown that approximately 90% of individuals with Ankylosing spondylitis test positive for HLA-B27. This correlation is crucial in clinical settings, as testing for HLA-B27 can aid in the diagnosis of this condition, especially in patients presenting with typical symptoms such as chronic back pain and stiffness.

While other HLAs listed in the choices, such as HLA-DR4, HLA-A1, and HLA-Cw6, are associated with different autoimmune diseases or conditions, they do not have the same strong association with Ankylosing spondylitis as HLA-B27 does. Understanding the role of HLA-B27 in Ankylosing spondylitis is essential for better diagnosis and management of the disease.