What is Juvenile-onset ankylosing spondylitis

Ankylosing spondylitis is often called arthritis of the spine. Ankylosing means stiffening of joints. Spondylitis means inflammation of one or more vertebrae (backbones).
Ankylosing spondylitis (AS) is a chronic, multisystem inflammatory disorder of the sacroiliac (SI) joints (between the segments of hip bones called sacrum and ilium) and the axial skeleton (the skeleton of the trunk and head).
When symptom onset occurs in individuals 2.
Ankylosing spondylitis with an age of onset of >17 years is termed adult-onset ankylosing spondylitis (AoAS).

Statistics on Juvenile-onset ankylosing spondylitis

Ankylosing spondylitis occurs in 0.2-0.8% of the population.
Among patients with ankylosing spondylitis, about 9-21% in white populations have a juvenile onset (less than 16 years old), whereas up to 40% of Mexican Mestizo and Korean patients have a similar early onset of the disease.

Risk Factors for Juvenile-onset ankylosing spondylitis

There is a strong genetic component to the disease – it tends to occur in families with a history of ankylosing spondylitis. It is highly associated with the antigen/protein called HLA-B27.

Progression of Juvenile-onset ankylosing spondylitis

There is a significant delay in the diagnosis of JoAS. A recent study showed that it was approximately 15 years from the start of symptoms to the diagnosis of juvenile-onset ankylosing spondylitis, whereas it took only about 7 years in adult-onset ankylosing spondylitis.
Patients with JoAS more commonly have symptoms in joints outside the trunk, and only later develop the characteristic spinal and sacroiliac involvement. They less commonly have low back pain and stiffness. Therefore, a young child with isolated complaint of the sacroiliac joint or lower back, an infection is more likely to be suspected than a JoAS.
Compared to AoAS, juvenile-onset ankylosing spondylitis involve fewer joints (usually fewer than 4). Hip and knee involvement is also more common in this group of patients.
Ankylosing spondylitis can affect the bowel and eye in addition to the heart, lungs and kidneys.

How is Juvenile-onset ankylosing spondylitis Diagnosed?

The doctor will perform some blood tests to check the blood cell count, markers for inflammation, the protein/antigen called HLA B27 which is present in most patients with ankylosing spondylitis but also in patients with other joint disorders (therefore not specific in diagnosing ankylosing spondylitis). Blood tests are not enough to make a diagnosis of ankylosing spondylitis.
Aspiration of joints (taking samples of cells from the joints under anaesthetics) may also be performed to look at the underlying process causing the symptoms.

Prognosis of Juvenile-onset ankylosing spondylitis

JoAS patients have a worse functional outcome (in terms of work disability, functional impairment, quality of life and spinal involvement) compared to adult-onset AS patients. For each year of disease the odds of becoming functionally impaired increased by 6 percent in those developing JoAS. Women with JoAS appear to develop functional impairment earlier than men with JoAS.

How is Juvenile-onset ankylosing spondylitis Treated?

The aims of treatment are to relieve pain and stiffness, maintain a maximal range of mobility and avoid the development of deformities. Education and appropriate physical activity are the cornerstones of management. Patients should be taught to perform regular daily back extension exercises, and to punctuate prolonged periods of inactivity with regular breaks. Swimming is ideal and should be encouraged. Poor bed and chair posture must be avoided.
Non-steroidal anti-inflammatory drugs (NSAIDs) are effective in providing symptomatic relief (pain and morning stiffness) but do not alter the course of the disease. The only disease-modifying agent with proven efficacy has been sulfasalazine, but its effect on disease in the trunk is minimal. Newer agents e.g. TNF-alpha inhibitors (etanercept and infliximab) are being tested in trials for their efficacy.

Juvenile-onset ankylosing spondylitis References

[1] Braun J, Bollow M, Remlinger G, Eggens U, Rudwaleit M, Distler A, et al. Prevalence of spondylarthropathies in HLA-B27 positive and negative blood donors. Arthritis Rheum 1998; 41: 58-67.
[2] Burgos-Vargas R, Pacheco-Tena C, Vazquez-Mellado J. Juvenile-onset spondyloarthropathies. Rheum Dis Clin North Am 1997; 23: 569-98.
[3] Burgos-Vargas R, Vazquez-Mellado J, Cassis N, Duarte C, Casarin J, Cifuentes M, et al. Genuine ankylosing spondylitis in children: a case-control study of patients with early definite disease according to adult onset criteria. J Rheumatol 1996; 23: 2140-7.
[4] Stone M, Warren RW, Bruckel J, et al. Juvenile-onset ankylosing spondylitis is associated with worse functional outcomes than adult-onset ankylosing spondylitis. A cross-sectional analysis. Arthritis Rheum 2005; 53:445-451.

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