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Challenge of the Unknowns—Unknown 2

Diagnosis and Discussion

DIAGNOSIS: Ankylosing Spondylitis

Follow-up and Treatment:

After a trial of conservative therapy that included light manipulation of the cervical spine and deep soft tissue work of the thoracic and lumbar paraspinal regions, the patients symptoms greatly reduced and the radiating pain once experienced often before is hardly ever felt anymore.


Diffuse Idiopathic Skeletal Hyperostosis (DISH) is often confused with ankylosing spondylitis. This case illustrated fused posterior elements of the lumbar spine, ankylosis of the entire length of the SI joints, and very thin ossification of the anterior spine. All of these qualities are inconsistent with DISH which will demonstrate sparing of the posterior elements, fusion of only the superior portion of the SI joints, if at all, and thick ossification of the anterior longitudinal ligament.

Two other conditions under the heading of "seronegative spondyloarthropathy" should have been given thought. These are psoriatic arthritis and Reiter's disease. They will have NON-marginal syndesmophytes that are asymmetric in nature and asymmetric involvement of the SI joints.

Ankylosing spondylitis is a chronic inflammatory condition that is part of the "seronegative spondyloarthropathies" (ankylosing spondylitis, psoriatic arthritis, Reiter's disease, and enteropathic spondyloarthropathy). The term seronegative pertains to the rheumatoid factor, therefore, even though this group of diseases may have radiographic similarities to rheumatoid arthritis due to their inflammatory nature, when blood work is obtained, rheumatoid factor will be negative. Regarding ankylosing spondylitis, another blood panel may be very helpful, Human Leukocyte Antigen (HLA) B27. About 90% of patients with ankylosing spondylitis will have a positive HLA B27. But be careful! This HLA B27 is not as specific or as sensitive as we would like because about 7% of the "normal" population will also have a positive HLA B27. The nonspecific ESR will also, in most cases, be elevated. This condition most often affects males (4:1 - 10-1) over females and most often begins between the ages of 20 and 30. While ankylosing spondylitis may affect virtually any joint in the skeleton, this disease has a definite predilection for the axial skeleton, classically originating both symptomatically and radiographically at the sacroiliac joints. The radiographic characteristics of ankylosing depend on the stage of the disease. These differing characteristics will be discussed according to the most affected body sites.

Sacroiliac Joints: The sacroiliac joints are classically the first portions of the skeleton to be affected by ankylosing spondylitis. The changes of sacroiliitis start at the lower margin of the sacroiliac joints due to the fact that this is the synovial portion of the joint. Radiographically, at first, the joint margins appear to be indistinct, somewhat widened, and sclerotic on the iliac side of the joint.

Bilateral Sacroiliitis

Later, as the disease progresses, the surrounding sclerosis becomes more evident and the joints slowly start to fuse from inferior to superior. Late stage AS

Fused SI Joints

entails complete fusion of the SI joints and the surrounding sclerosis slowly subsides. The distribution of these changes is classically bilateral and symmetric as is the distribution in other joints, however, at the very beginning of the disease these changes may be bilateral, but asymmetric, simulating a pattern more typical of other inflammatory diseases such as rheumatoid arthritis, psoriatic arthritis, or Reiter's disease.

Spine: Syndesmophytes, representing ossification of the outer anulus of the intervertebral disc, ankylosing spondylitis and usually begins at the thoracolumbar junction. Many times, before these syndesmophytes are visualized, other manifestations of the spine may be noted. These early changes include "square" or "barrel" shaped vertebral bodies

Square vertebral bodies

(loss of the normal anterior concavity) due to erosions of anterior portions of the superior and inferior vertebral bodies, so-called Romanus lesions. These lesions will eventually heal with sclerosis, the "shiny-corner" sign. Later changes to the spine include syndesmophyte formation as previously discussed. These changes typically start at the thoracolumbar junction, then typically to the lower lumber region, then eventually these syndesmophytes will ankylose the spine in a cephalad direction. Not only will the anterior portion of the vertebral segments will fuse, but the posterior elements will also fuse from inferior to superior

Fusion of the facet joints

This fact differs from DISH which does not affect the facets. Regarding the upper cervical spine, ankylosing spondylitis is known to rarely affect the transverse ligament due to its inflammatory nature leading to instability of C1 resulting in a possible neurological deficit. Due to this fact, all patients with AS should have flexion and extension cervical views obtained.

Extremities: While the axial skeleton is the most predominant site of involvement in patients with AS, the extremities will also be involved in about 20%-50% of the cases. As in the SI joints the classic distribution of lesions in the extremities is bilateral and symmetric. The extremity joints most commonly involved with AS are the "root joints", hips and shoulders. The hip joints are the most affected extremity and most often represents a poor prognosis. The radiographic signs of hip involvement include axial migration of the femoral head in a bilateral and symmetric distribution.

Hip joint involvement

This pattern is also seen in rheumatoid arthritis and calcium pyrophosphate deposition disease (CPPD). Distinguishing features include osteophytosis along the lateral aspect of the femoral head that is not seen in rheumatoid arthritis and lack of sclerosis and calcification seen in CPPD.

Other systems: The inflammatory nature of ankylosing spondylitis does not limit itself to only the skeletal system in many cases. Other systems that may be involved are the heart (cardiomegaly and pericarditis) and lungs (pulmonary fibrosis). Prostatitis has been noted in approximately 80% of males with AS. Iritis has been noted in about 20%-25% of cases. Renal failure is also a known, albeit uncommon, complication secondary to amyloidosis. Spinal cord complications include arachnoid diverticula and may cause radiating pain down the legs. There is a mysterious connection between inflammatory bowel disease and AS type spinal changes. Approximately 5%-15% of patients with inflammatory bowel disease , most commonly Crohn's disease or ulcerative colitis, will develop these changes of the spine, termed enteropathic spondylitis. Interestingly, patients with known AS will occasionally (up to 17% in one study) develop an inflammatory disease, however, this correlation is not supported by some authorities. As you remember the patient in this unknown case did indeed develop ulcerative colitis. Pure coincidence? Nobody will ever know!


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Introduction to Unknown Cases

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