**Question:** Not true about Ankylosing spondylitis

A. Ankylosing spondylitis (AS) is a chronic inflammatory disorder affecting the axial skeleton, causing pain, stiffness, and limited mobility.
B. The disease primarily affects the sacroiliac joints and spine, leading to fusion and reduced mobility.
C. There is no association between AS and genetic markers like HLA-B27.
D. Patients with AS always have severe spinal deformities and disability.

**Core Concept:** Ankylosing spondylitis (AS) is a chronic inflammatory disorder, primarily affecting the axial skeleton, especially the sacroiliac joints and spine. AS is associated with the presence of specific genetic markers, such as HLA-B27, which is why option C is incorrect.

**Why the Correct Answer is Right:** AS is a complex disease, involving both genetic and environmental factors. The association with HLA-B27 is a genetic marker that increases the risk of developing AS but is not a guarantee for its occurrence. The disease affects the axial skeleton, causing inflammation, pain, and limited mobility, leading to fusion and deformities in severe cases. However, not all AS patients develop severe spinal deformities and disability.

**Why Each Wrong Option is Incorrect:**

A. While AS primarily affects the axial skeleton, particularly the spine and sacroiliac joints, the disease does not affect other joints and organs extensively. The statement that AS affects only the sacroiliac joints and spine is inaccurate.

B. AS does lead to spinal fusion and deformities in severe cases, but not all patients develop these complications. The statement that AS causes severe spinal deformities and disability in all patients is not true.

C. The association between AS and HLA-B27 is a genetic marker that increases the risk of developing AS. Some patients with AS may not have HLA-B24, making this statement incorrect.

E. The statement that AS affects only the sacroiliac joints and spine is incorrect, as AS primarily involves the axial skeleton, including the spine, but also affects other joints, such as the sacroiliac joints, hips, and sometimes shoulders.

**Clinical Pearl:** Although genetic markers like HLA-B27 are associated with AS, the disease affects the axial skeleton, not just the sacroiliac joints and spine. Understanding the genetic predisposition and the clinical manifestations of AS, including joint involvement, is essential for accurate diagnosis and management of patients.