Cauli, Alberto and Vacca, Alessandra and Mameli, Antonella and Fiorillo, Maria Teresa and Passiu, Giuseppe and Sorrentino, Rosa and Mathieu, Alessandro (2007) The First description of a patient with ankylosing spondylitis (AS) positive for the AS-not associated allele B*2709, but also for two alleles associated with the disease. Rheumatology, Vol. 46 (Suppl. 1), p. i51. eISSN 1462-0332. Article.
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Background: The B*2709 allele, first described among the Italian population, has
been found not to be associated with AS in the Sardinian and in continental Italy
populations. It has been reported to be present in few cases seronegative
peripheral arthritis without axial involvement. If the B*2709 subtype is actually not
associated with AS and has a neutral role in the development of the disease, like
any other AS-unrelated allele of B locus, the presentation of sporadic B*2709þ AS
patients is to be expected by chance, and should be regarded as a case of B27-
negative AS, but has never been reported.
Methods: A 36-yr-old sardinian woman presented for chronic low back pain and
stiffness since the age of 30. The onset was reported to be insidious, characterized
by lumbar pain and early morning stiffness; the pain was also present bilaterally in
the gluteal area and in the sacroiliac (SI) region, and was irradiated to the lower
limbs down to the dorsal thigh, and alternate from side to side. Conventional
radiography showed erosions in the iliac and sacrum side of the SI joint and mild
sclerosis of the subcortical bone, bilaterally on the iliac sides. CT scan of the SI
joints confirmed bilateral irregular articular profiles on both iliac and sacrum sides
due to marginal erosions, and mild sclerosis of iuxtaarticular iliac bone. SI joint MRI
confirmed the diagnosis. HLA typing was: A23, 23; B14, *2709; CW1, 8; DRB1* 13,
16; DQA1 0102, 0102; DQB1 05, 05. The HLA-B14 subtyping was B*1403.
Results: Recent reports suggest to take into consideration all the alleles of the
HLA-B locus, since it is emerged that in B27-negative AS patients some B alleles
are associated with the disease; this is the case of the B*1403 subtype in a West
African population. These alleles may be related with AS, like B27 ‘susceptible’
subtypes, either for an intrinsic pathogenetic role or for the proximity to another
gene directly responsible for the susceptibility to the disease. Thus, in the patient
described, susceptibility to AS may be related to the presence of this AS-associated
allele rather than to B*2709, which in this case would have a ‘neutral’ role.
Furthermore, it is noteworthy that the patient has another allele, the HLA-DR16,
which has been found to be present in the extended haplotype that in Sardinia is
strongly associated with AS. The peculiar mixed phenotype of this patient,
whose family is currently under investigation, makes her a good subject to study in
the search for AS genetic susceptibility factors.
Conclusions: In conclusion, this is the first observation of the presence of the
HLA-B*2709 subtype in a patient with AS. However, the peculiar HLA phenotype of
this patient suggests caution in interpreting these results because of the presence
of other alleles, B*1403 and DR16, involved in the susceptibility to AS.
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