Diagnosing axial SpA [Ankylosing Spondylitis (AS) and
undifferentiated SpA(uSpA) with predominant axial
involvement but without radiographic sacroiliitis] in the
absence of radiographic sacroiliitis poses a major challenge
to many physicians. In the absence of diagnostic criteria,
classification criteria are often used to aid the diagnostic
process in daily practice. The most often cited classification
criteria for SpA are the Europian Spondylarthropathies
Study Group (ESSG) criteria that were proposed in 1991.
According to these criteria, in the absence of sacroiliitis; patients with inflammatory spinal pain or synovitis
(asymmetric, predominantly in the lower limbs) in
addition to any one of the following (positive family
history, psoriasis, inflamatory bowel disease, alternate
bottock pain, enthesopathy) are classified as seronegative
SpA with 77% sensitivity and 89% specificity. In the
presence of sacroiliitis, sensitivity is 86% and specificity is
87%
1. However in a recent study from Spain, it was
observed that the performance of the ESSG criteria as
diagnostic criteria in daily practice was moderate: only
46.6% of patients with possible SpA who met the ESSG
criteria at entry into the study were judged by their
rheumatologist to have SpA after 5 years of follow up
2.
The typical radiographic changes of AS are seen primarily
in the axial skeleton, especially in the sacroiliac,
discovertebral, apophyseal, costovertebral, and
costotransvers joints
3. Syndesmophyits seen in AS and
entheropathic arthiritis are usually symmetrical and
bilateral, while that are seen in reactive arthiritis and
psoriatic arthritis are nonmarginal, rough and
asymmetrically located
4. The radiological appearance
of arthritic changes in sacroiliac joints has been regarded
as a hallmark of AS according to Modified New York
Criteria
5. In AS patients in addition to sacroiliitis,
arthritic changes in the spine visualized by x-ray develop
in 57- 88% of the patients
6,7. In literature, there were
AS patients with typical clinical features but no radiological
sacroiliitis
8. Khan et al reported that radiographic
sacroiliitis is frequent in AS but is not an early or obligate
manifestation of the disease. In particular, relatives of AS
with IBP may not show radiographic sacroiliitis even after
long follow-up
9. Rudwaleit reported that in a small
proportion of AS patients may never develop
radiolographic sacroiliitis despite having IBP for many
years. SpA patients with predominantly axial symptoms
should be considered as having a same disease entity as
AS patients, independent from the presence of
radiographic sacroiliitis
10. In one study 60% of SpA patients had developed definite AS after 10 years of
follow-up. It took an average of 9 years (+/-6 years) for
radiological sacroiliitis to appear in these patients. A
further 20% still had chronic uSpA and might have
developed radiological sacroiliitis if their follow-up had
been continued for a longer time
11. Again in another
family study, radiographic evidence of sacroiliitis was
found in 40% of patients with a symptom duration of
<10 years, 70% with symptoms for 10-19 years, and 86%
with symptoms for ≥ 20 years
12. The morphological
changes used to assess spinal involvement in x-ray were
syndesmophytes, shining corners, squaring, arthritis of
the apophyseal joints, spondylodiscitis, bamboo spine
and trolley track sign
13. Descriptions of spinal x-ray
changes typical of AS without concomitant radiological
sacroiliitis are thus relatively uncommon. Besides, Moll
reported that these spinal x-ray changes develop later in
the course of AS and usually after radiological sacroiliitis
is evident.
14. MRI is considered to be very helpful in
detecting signs of sacroiliitis that are not yet visible in
x-ray
15. Although our HLA B27 positive patient has
been suffering from IBP for 10 years, no sacroiliitis was
detected in her pelvic x-ray and MRI. However in her
throracic and lomber x-ray, all radiological abnormalities
such as squaring, shiny corner, syndesmophytes, bamboo
spine, trolley track sign were clearly present. In her foot
x-ray, bilateral calcaneal enthesopathy was detected.
It has recently been showed that patients with early
disease without radiographic sacroiliitis (uSpA with axial
involvement) do not differ in this regard from patients
with definite AS (with radiographic sacroiliitis) of short
duration (<10 years) with respect to disease activity (as
evaluated by BASDAI)16. In our case; BASDAI score was
6.7 and the disease was considered active also.
Depending on all these findings; we want to focus on
the possibility of patients with long term
spondyloarthropathies features who have typical
radiographic changes of axial spondylitis without sacroiliitis.
That is why we strongly believe the importance of the
classification criteria in order to avoid misclassification.
Conflict of Interest
No conflict of interest is declared by authors.
)
)
)
)
)
