Undifferentiated Spondyloarthropathy

Undifferentiated Spondyloarthropathy is a term used to describe the condition where presentation does not meet the criteria for a definitive diagnosis of ankylosing spondylitis or related disease.

Undifferentiated spondyloarthropathy may represent an early phase or incomplete form of ankylosing spondylitis or another spondyloarthropathy. However, more recent data suggest that these patients may represent a distinct disease entity based on demographic and clinical criteria.

Before understanding undifferentiated spondyloarthropathy, one must have an idea about seronegative spondyloarthropathies.

[Read more about seronegative spondyloarthropathies]

Pathophysiology of Undifferentiated Spondyloarthropathy

Pathophysiology of undifferentiated spondyloarthropathy is similar to other spondyloarthropathies. Read ankylosing spondylitis for detailed pathophysiology.

Differentiating features are given below

Distinguishing Features of Undifferentiated spondyloarthropathy from Other Spondyloarthropathies

• In contrast to other spondyloarthropathies, the age of onset in case of undifferentiated spondyloarthropathy has a very wide range. The peak age of onset is approximately 50 years.
• More females are affected than males. The male-to-female ratio is 1:3.
• Not much radiological changes are seen with the passage of time. Sacroiliitis and spondylitis are either absent or appear very mild on routine radiography.
• Extraarticular manifestations are less, occurring in fewer than 10% of patients, and include acute anterior uveitis (1-2%), oral ulcers, rash, nonspecific IBD, pleuritis, and pericarditis.
• HLA-B27 antigen is positive only in approximately 20-25% of patients.

Late age of onset, female predominance, and low HLA-B27 positivity suggest that undifferentiated spondyloarthropathy is distinct from ankylosing spondylitis and the other classic spondyloarthropathies.

It was earlier believed that this condition represents an initial stage in the development of specific spondyloarthropathies but when these patients are observed over long periods, they rarely develop clinical manifestations or radiographic changes that result in a change of diagnosis.

Clinical Presentation of Undifferentiated Spondyloarthropathy

There are various kinds of presentation. About 90%  of the patients have inflammatory back pain

Inflammatory back pain has following features

• Insidious onset
• > 3 months of symptoms before presentation
• Morning stiffness lasting at least 30 minutes, improvement of symptoms with moderate physical activity
• Diffuse nonspecific radiation of pain into both buttocks
• Patients may wake up in the morning with pain and stiffness

More on inflammatory back pain

About 80% of the patients have buttock pain – 80%

Enthesitis is present in  85%. Pain at the site of enthesitis like the back of the heel [Achilles tendon insertion], heel [ plantar fasciitis] occurs in 30-50% of the cases.

In about 35%, pain is reported mainly in the hips, shoulders, and joints of the chest wall, including the acromioclavicular and sternoclavicular joints. Other peripheral joints are involved less frequently and to a milder degree.

About 15% of patients report dactylitis which means inflammation of a digit.

More than half of the patients also complain of fatigue.  [

The examination of the patient is conducted in the same pattern as in ankylosing spondylitis to look for chest expansion, spine stiffness, tenderness at the entheses and joint stiffness. For details article on ankylosing spondylitis can be consulted.

Diagnosis of Undifferentiated Spondyloarthropathy

Although no specific criteria are identified, using modified Amor criteria can be helpful.

Lab Studies

Lab studies are usually normal except for inflammatory markers like ESR and CRP in about 30 percent of the cases.

HLA B27 is present only in 25% of the cases.

Imaging

Unlike ankylosing spondylitis, the radiological changes are not pronounced in undifferentiated spondyloarthropathies.  Occasionally, X-ray may show evidence of periosteal new bone formation at sites of enthesitis. Enthesitis. Insertion of the Achilles tendon or plantar fascia on the calcaneus is particularly are more involved. X-rays may also show early syndesmophytes on the lumbar spine without bridging.

Treatment of Undifferentiated Spondyloarthropathy

Most of the patients [>75%] with undifferentiated spondyloarthropathy have chronic, active disease. They require long-term therapy.

Few of them have mild and symptoms which are also intermittently present. These episodes may last from 1-2 weeks to several months, interspersed with the long asymptomatic period. These patients require intermittent symptomatic therapy. The patient does not require the therapy during the asymptomatic period.

The treatment is generally on the same principles as in cases of ankylosing spondylitis. The intensity of the treatment would be guided by the symptoms.

Nonsteroidal anti-inflammatory drugs are effective in most of the patients and patients maintain good function without progressive disease or clinically significant radiographic changes.

A small percentage of the patients do not respond to NSAIDs well. In these patients, treatment is similar to patients with ankylosing spondylitis, including the use of sulfasalazine, methotrexate, and TNF-alpha antagonists.

Patients are advised to maintain an active lifestyle and undertake an exercise to reduce stiffness and maintain mobility.