Systemic lupus erythematosus and rheumatoid arthritis

Type 
Age of onset 
No. of ACR 
criteria 
SLICC/ACR 
index 
SLEDAI 
score 
PvuII
C allele / 
PvuII
TT 
40.6 (1.2)*/
35.7 (1.7) 
5.6 (0.1) /
5.5 (0.1) 
2.3 (0.2) /
2.5 (0.3) 
3.5 (0.3) /
3.4 (0.6) 
XbaI
G allele / 
XbaI
AA 
40.0 (1.4) /
38.2 (1.3) 
5.6 (0.1) /
5.5 (0.1) 
2.0 (0.2)* /
2.7 (0.2) 
3.2 (0.4) /
3.6 (0.4) 
* p<0.05, all analysed by Student’s 
t
test 
The C allele of the 
PvuII
polymorphism has previously been found associated 
with older age for disease onset, which compliments our results.
199
The function of the 
PvuII
and 
XbaI
polymorphisms are unknown. Both SNPs 
are intronic and there are reports that the 
PvuII
C allele produces a binding site 
for the myb family of transcription factors. In presence of B-myb there was a 
four times greater expression of a downstream reporter construct compared with 
that seen for the 
PvuII
T allele.
200; 201
The 
PvuII
C allele could upregulate the 
expression of OR
α
or alter the transcript, thus explaining the genotype-
phenotype correlations. The role of 
XbaI
is unknown, except for being in high 
LD with 
PvuII
. 
In summary: The two polymorphisms, 
PvuII
and 
XbaI
, of the OR
α
gene were 
not associated with SLE 
per se
. However, the minor alleles, 
PvuII
C and 
XbaI
G, were associated with a milder form of the disease represented by skin 
manifestations, later disease onset and a lower SLICC index score. The major 
alleles, 
PvuII
T and 
XbaI
G, were associated with a more severe disease 
represented by serositis, cognitive impairment, angina/coronary artery bypass, 
earlier disease onset and a higher SLICC/ACR damage index score.