Ankylosing Spondylitis

A chronic, inflammatory condition that typically begins in the sacroiliac region and extends up the spine. 

Demographics

Age at onset: 15-35 years

Sex: male to female ratio of 10:1

Prevalence: 0.15% of male population

Clinical Presentation

•       Morning stiffness, especially in the spine

•       Bilateral sacroiliac tenderness

•       Limited lumbar spine mobility

•       Decreased chest expansion

•       Occasionally, peripheral, large joint involvement

•       Systemic effects in severe cases include fatigue, anorexia, weight loss, cardiovascular and pulmonary manifestations

•       “question mark” deformity or “bamboo spine” in later stages characterized by increased thoracic kyphosis and decreased lumbar lordosis

Differential Diagnosis

Criteria for diagnosis include:

•       Low back pain for at least 3 months; improved with exercises but not relieved with rest

•       Limited lumbar spine mobility

•       Decreased chest expansion below normal values for age and sex

•       Bilateral sacroiliac tenderness, minimal or greater

•       Unilateral sacroiliac tenderness, moderate or greater

•       Lab tests: elevated sedimentation rate, absent rheumatoid factor, presence of HLA B27 antigen

•       Imaging: vertebral bodies may become demineralized, calcification of the annulus fibrosus and spinal ligaments, fixed kyphosis

Clinical Bottom Line: Treat and Refer

References:
Please refer to the "Ankylosing Spondylitis" section of the reference list.