eMedicine Specialties > Neurology > Inflammatory and Demyelinating Diseases

Ankylosing Spondylitis

Author: Alan Schaffert, MD, Former Chief of Staff, Department of Medicine, Doctor's Medical Center of Modesto; Clinical Assistant Professor, University of California at Davis
Contributor Information and Disclosures

Updated: Jan 8, 2007

Introduction

Background

Spondyloarthritis or spondyloarthropathy refers to a group of chronic inflammatory conditions affecting the joints, tendon and ligament attachments, and sometimes nonskeletal structures. Ankylosing spondylitis (AS) is one of these inflammatory diseases. It primarily affects the axial joints, including the spine and sacroiliac joints. It causes eventual fusion of the spine. Peripheral joints may be involved.

Pathophysiology

Inflammation at the sites of insertion of ligaments and tendons in the bones is the primary pathological process. Reactive bone growth occurs that is cumulative with each new attack. The disorder is predominantly skeletal, with ankylosis of the spine; involvement of hips, knees, and occasionally small joints; and plantar fasciitis.

Nonskeletal problems associated with AS may include iritis, uveitis, aortitis, pulmonary fibrosis, amyloidosis, and inflammatory bowel disease. Neurological complications include C1-C2 subluxation, tendency to spinal fractures with minor trauma, spinal stenosis in the cervical or lumbar regions, chronic inflammatory cauda equina syndrome, and radiculopathy secondary to fracture or compression.

Frequency

United States

In the general population, 1.4% are affected.

Sex

Male-to-female ratio is approximately 3:1.

Age

Peak onset is in adolescents and adults aged 15-30 years. A juvenile form also exists.

Clinical

History

Patients typically present in their late teens or twenties. Large joints of the lower extremities are involved more commonly in the juvenile form than in the adult form.

  • Patients usually describe a gradual onset of low back pain over 3 or more months. The pain is described as follows:
    • Worse in the morning with improvement during the day
    • Better with activity and worse with rest (helps in distinguishing AS from mechanical low back pain)
    • Gradual ascending pattern from the lumbar region to the thoracic and then the cervical spine
  • Approximately 25% of patients present with complaints of proximal joint involvement. Rarely, small joint involvement is a presenting feature.
  • Patients may describe pain and stiffness of the rib cage, which may or may not be pleuritic in nature. Atypical chest pain may be present.
  • Presentation may be atypical or as a forme fruste.

Physical

  • Examine for tenderness over the sacroiliac joints. Look for loss of lumbar lordosis and limited range of lumbar motion. In early phases of the disease, range of motion limitations may be due to muscle spasm. However, later it is due to bony fusion.
  • Measure for limitations in chest expansion.
  • Range of motion of the entire spine may be limited. In chronic, untreated cases, thoracic kyphosis is increased. This results in a characteristic posture in which the patient cannot look to the horizon.
  • Acutely involved joints may have overlying purplish discoloration.

Causes

  • About 90-95% of patients have the HLA-B27 antigen.
  • Onset and flare-ups may be due to poorly understood environmental factors.
  • Presumably, a fairly benign bacterium or virus can be antigenically similar to human ligaments.
  • In a susceptible individual, a mild infection might stimulate an abnormal immune response.

More on Ankylosing Spondylitis

Overview: Ankylosing Spondylitis
Differential Diagnoses & Workup: Ankylosing Spondylitis
Treatment & Medication: Ankylosing Spondylitis
Follow-up: Ankylosing Spondylitis
References
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References

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Further Reading

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Keywords

ankylosing spondylitis, Marie-Strümpell arthritis, Bechterew disease, spondyloarthritis, spondyloarthropathy, chronic inflammatory conditions, AS, inflammation of the joints, inflammation of the tendons, inflammation of the ligaments, iritis, uveitis, aortitis, pulmonary fibrosis, amyloidosis, inflammatory bowel disease

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Contributor Information and Disclosures

Author

Alan Schaffert, MD, Former Chief of Staff, Department of Medicine, Doctor's Medical Center of Modesto; Clinical Assistant Professor, University of California at Davis
Alan Schaffert, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, California Medical Association, and National Stroke Association
Disclosure: Nothing to disclose.

Medical Editor

Rodrigo O Kuljis, MD, Esther Lichtenstein Professor of Psychiatry and Neurology, Director, Division of Cognitive and Behavioral Neurology, Department of Neurology, University of Miami School of Medicine
Rodrigo O Kuljis, MD is a member of the following medical societies: American Academy of Neurology and Society for Neuroscience
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Florian P Thomas, MD, MA, PhD, Drmed, Director, Spinal Cord Injury Unit, St Louis Veterans Affairs Medical Center; Director, National MS Society Multiple Sclerosis Center; Associate Program Director, Professor, Department of Neurology and Psychiatry, Associate Professor, Institute for Molecular Virology, and Department of Molecular Microbiology and Immunology, St Louis University
Florian P Thomas, MD, MA, PhD, Drmed is a member of the following medical societies: American Academy of Neurology, American Paraplegia Society, and National Multiple Sclerosis Society
Disclosure: Nothing to disclose.

CME Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.

Chief Editor

Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Nicholas Y Lorenzo, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Neurology
Disclosure: Nothing to disclose.

 
 
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