Radiology Teaching Files > Case 4405918

Contributed by: Virginia Mason Medical Center.
Patient: 26 year old female

26 y/o F p/w 2-3wk h/o aching pain in collar bone and sternum/precordium; ROS + occasional morning stiffness in the lower back and hips.

1. Asthma.
2. Hay fever.
3. Acne.

1. Singulair 10 mg daily.
2. Claritin 10 mg daily.
3. Yasmin birth control pills.
4. Prilosec 20 mg daily.

Unknown. She is adopted.


Fig. 1: 26 y/o F, HLA-B27 positive. Sacroiliitis.

ANA: spiculated 1:20
CRP: 46
RF: neg
HLA-B27: positive
Pelvic film: Bilateral symmetrical sacroiliitis with slight irregular widening of the joint space suggesting underlying cartilaginous destruction.

Sacroiliitis, bilateral; in pt with HLA-B27 / ankylosing spondylitis.

Ankylosing spondylitis affects synovial and cartilaginous joints as well as sites of tendon and ligament attachment to bone (entheses). An overwhelming predilection exists for involvement of the axial skeleton, especially the sacroiliac, apophyseal, discovertebral, and costovertebral articulations. Classically, changes are initially noted in the sacroiliac joints and next appear at the thoracolumbar and lumbosacral junctions. With disease chronicity, the remainder of the vertebrae may become involved. However, this characteristic pattern of spinal ascent is by no means invariable; it may occur slowly or rapidly, and is less frequent in spondylitis accompanying psoriasis and Reiter's disease.

Sacroiliitis is the hallmark of ankylosing spondylitis. It occurs early in the course of the disease. Although an asymmetric or unilateral distribution can be evident on initial radiographic examination, roentgenographic changes at later stages of the disease are almost invariably bilateral and symmetric in distribution. This symmetric pattern is an important diagnostic clue in this disease and may permit it differentiation from other disorders that affect the sacroiliac articulation, such as RA, psoriasis, Reiter's syndrome, and infection. Changes in the SI joint occur in both the synovial and ligamentous (superior) portions, and predominate on the iliac side, for reasons that are obscure.


Richardson, M.  Approaches To Differential Diagnosis In Musculoskeletal Imaging.  Axial Arthritis., April 17, 2006

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Additional Details:

Case Number: 4405918Last Updated: 04-17-2006
Anatomy: Skeletal System   Pathology: Non-Infectious Inflammatory Disease
Modality: Conventional RadiographExam Date: Access Level: Readable by all users
Keywords: sacroiliitis, seronegative spondyloarthropathy, hla-b27

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