Ankylosing spondylitis differential diagnosis, investigations,prognosis, treatment

Here is the second part of the discussion of Ankylosing spondylitis (AS), in which we are going to discuss the differential diagnosis (DD), investigations and treatment .
- Definition, causes, pathology and clinical picture of Ankylosing spondylitis is Here

Differential diagnosis of Ankylosing spondylitis (AS)

• The inflammatory back pain of AS is usually distinguished by the following features.
- Age of onset < 40 years - Insidious onset
- Duration > 3 m - Improvement with exercise.
AS must be differentiated from other causes of bachache (see later).
• Diffuse idiopathic skeletal hyperstosis (DISH) must be differentiated from AS .as it leads to marked calcification and ossification of paraspinous ligaments.


1- X ray Sarco-iliac joint :  erosion, sclerosis. It is often the first abnormality.
2- X ray Spine (The disc is preserved, unlike in spondylosis).
   • Square shaped vertebrae.
   • Calcification of longitudinal ligament.
   • Bony bridging between vertebral bodies = syndesmophytes ==> bamboo spine.
3- Laboratory finding (there is no specific laboratory test).
   • Normochromic anemia.
   • ESR +++ ,+++ CRP during activity.
   • Rheumatoid factor -ve.
   • HLA Testing is rarely of value because of the high frequency of HLA-B27 in the population.
   • Alkaline Phosphatase l' with activity .

Treatment of Ankylosing spondylitis

(The principles are to relieve pain and spinal stiffness).
• The key of treatment is early diagnosis to start preventive exercise program before syndesmophytes have formed. Excercises aim to maintain spinal mobility, posture and chest expansion (swimming is recommended).
• NSAIDs :  relieve symptoms, but don't alter the course of the disease
• Local steroid :  for enthesopathy and planter fasciitis.
• Genetic counselling.
• Systemic steroid sometimes required for treatment of uveitis.
• Sulfasalazine and methotrexate may be of value for peripheral arthropathy.
• TNF blockers are effective
• Surgery: plaster jackets to correct kyphosis, hip arthroplasty.
With exercise and pain relief, the prognosis is excellent and over 80% of patients are employed.
Ankylosing spondylitis differential diagnosis, investigations,prognosis, treatment
Dr.Tamer Mobarak


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