Final answer:
Ankylosing spondylitis is a chronic systemic inflammatory disorder affecting the spine, not described by kyphosis, scoliosis, or lordosis. These latter conditions involve abnormal curvatures of the spine and can be caused by multiple factors, including growth abnormalities and osteoporosis.
Step-by-step explanation:
The cause of Ankylosing spondylitis is idiopathic and is defined as a chronic systemic inflammatory disorder that primarily affects the spine. It is not characterized by an increase in the normal thoracic curve (kyphosis), a lateral rotatory deviation of the spine (scoliosis), nor an increase in normal lumbar curve (lordosis) with an anterior pelvic tilt. Ankylosing spondylitis mainly involves inflammation where ligaments and tendons attach to bone, leading to pain and stiffness, particularly in the spine.
Disorders of the spine, such as kyphosis, lordosis, and scoliosis, affect the curvature of the spine. Kyphosis results in a hunchback or humpback appearance due to an excessive posterior curvature of the thoracic region. Lordosis is characterized by an excessive anterior curvature of the lumbar region, often associated with late pregnancy or obesity. Scoliosis is an abnormal lateral curvature that can also involve twisting of the vertebral column. These conditions can result from various causes including poor posture, abnormal growth, bone diseases such as osteoporosis, and developmental anomalies.