Test: Ankylosing Spondylitis - NEET PG MCQ

The clinical symptom of a young male experiencing low back pain, which worsens in the morning but improves with physical activity by the evening, suggests a potential diagnosis of ankylosing spondylitis.

• Patients may develop costochondritis over time, resulting in restricted chest expansion.
• The most distinctive findings include a reduction in spinal mobility, characterised by limitations in both anterior and lateral flexion, as well as extension of the lumbar spine and chest expansion.
• Ankylosing spondylitis is associated with bone marrow oedema.

Rheumatoid arthritis is more prevalent among middle-aged women, with a ratio of males to females of approximately 1:3, and typically involves peripheral polyarthritis that affects the small joints of the hand symmetrically.
Clinical features of ankylosing spondylitis

1. Early Diagnostic feature: decreased chest expansion (<3.8 cm). Chest expansion Is measured as the difference between maximal Inspiration and maximal forced expiration in the fourth intercostal space in males or just below the breasts in females, with the patient's hands resting on or Just behind the head. Normal chest expansion is >5 cm.
2. Patient walks in a stooped position and has essentially no motion in the spine.
3. Extra-articular features: iritis, cardiac conduction defects, aortic incompetence, spinal card compression & amyloidosis.

Investigations

• Rheumatoid factor and serologic tests: negative.
• Radiographic appearance of the spine:
  a. Early stages: Lower lumbar disc degenerative condition with sacroiliac joint involvement.
  b. End-stage disease: Sacroiliac joints are fused.
  c. Squaring of vertebral bodies & development of delicate syndesmophytes.
  d. Complete fusion with a bamboo spine appearance
• HLA B27: Positive

The image displays the modified Schober test being performed to assess ankylosing spondylitis. In situations where chest wall motion is restricted, it is typical to observe:

• Reduced vital capacity
• Increased functional residual capacity

The distance increases by more than 5 cm if mobility is normal and by less than 4 cm if mobility is reduced. Chest expansion is calculated as the difference between maximal inspiration and maximal forced expiration, measured in the fourth intercostal space for males or just below the breasts for females, with the patient's hands positioned on or just behind the head. Normal chest expansion is less than 5 cm.

AS demonstrates a notable association with the histocompatibility antigen HLA-B27 and is found globally, largely corresponding to the prevalence of B27.

• Approximately 90% of individuals with AS possess the HLA-B27 antigen.
• This correlation exists regardless of the severity of the disease.

Over 90% of instances of SLE occur in women, often beginning at childbearing age. The presence of exogenous hormones has been linked to the onset and exacerbation of lupus, indicating that hormonal elements may play a role in the disease’s pathogenesis.

• The likelihood of developing SLE in men is comparable to that in prepubescent or postmenopausal women.
• Notably, in men, SLE is more prevalent among those with Klinefelter syndrome (i.e., genotype XXY), which further supports the hormonal theory.
• The female-to-male ratio peaks at 11:1 during the childbearing years.
• A correlation exists between age and SLE incidence, reflecting the peak years of female sex hormone production.

In contrast, AS is generally diagnosed more often in males, with a male-to-female ratio of 3:1.

In AS, joint involvement typically arises most frequently in the hips, shoulders, and the joints of the chest wall, which encompass the acromioclavicular and sternoclavicular joints. This often manifests within the initial 10 years of the condition.

• Damage to the joints, particularly in the hips and shoulders, can lead to radiographic changes.
• Individuals with juvenile-onset AS are more likely to experience involvement of the hip and shoulder joints compared to adult patients with AS.

Conduct the Schober test by marking a 10-cm segment of the lumbar spine (with the patient standing upright), beginning at the fifth lumbar spinous process. Instruct the patient to flex their spine to the maximum extent. Remeasure the distance between the marks. Normal flexion should result in an increase of at least 5 cm in the distance.

• Those with long-standing disease, including some with complete spinal ankylosis, have experienced notable improvements in both objective and subjective measures of disease activity and function.
• This includes reductions in morning stiffness, pain, spinal mobility, peripheral joint swelling, CRP, and ESR.

• Stiffness and discomfort can awaken patients in the early morning, a characteristic symptom not typically observed in those with mechanical back pain.
• Inflammatory back pain is the predominant symptom and the initial sign in around 75% of patients.
• The pain is usually dull and poorly localised to the gluteal and sacroiliac (SI) regions.
• Pain often starts unilaterally and intermittently, typically beginning in the lumbo-sacral area.