Background Systemic lupus erythematous (SLE) represents a heterogeneous group of patients. Some of them are diagnosed with SLE with mild articular and cutaneous symptoms, while others present with severe organ damage. There are also patients with positive ANA and clinical manifestations of SLE, but who don’t fulfill classification criteria for SLE (1). They are classified as incomplete lupus erythematosus (ILE) (1). Some of them will develop SLE, but currently there is no way to identify them. The aetiology and pathogenesis of systemic lupus erythematosus (SLE) are not completely understood, but it is likely a multifactorial disease, where genetic factors play an important role. To date, the strongest genetic association has been found at genes for class II human leukocyte antigens (HLA), particularly HLA-DR2 (HLA-DRB1 alleles) and HLA-DR3 (2).

Objectives To ascertain the HLA DRB1 alleles frequencies in Caucasian patients with SLE and in patients with ILE, and compare them between both groups.

Methods A case-control study was designed to find out the frequency of the HLA- DRB1 alleles in ILE patients, comparing them to LES patients who were used as controls. For this purpose, 120 patients were recruited from the outpatient clinic of the CHUVI (Spain), 60 with SLE and 60 with ILE. Patients presenting with ANA antibodies (>1/320) and one or two classification criteria for SLE, but without any manifestations of other autoimmune disease after >2 years of follow-up, were considered as having ILE. All patients have been interviewed and data about their illness have been retrieved from their clinical records. Blood samples were taken from all the patients. DNA extraction was performed from peripheral blood leukocytes, and HLA DRB1 alleles were amplified by PCR, using previously reported primers (3).

Results After HLA DRB1 typing of our 120 patients, frequencies showed below were obtained.

Both groups showed similar frequencies for all the studied alleles except one. HLA DRB1*15 was more frequent in SLE group than in ILE group (p-value 0,0254).

Conclusions HLA DRB1*15 has been found more frequently in SLE patients than in ILE group. If this finding is corroborated by larger studies, HLA DRB1*15 could be used to identify those patients diagnosed with ILE who are at higher risk to develop SLE.

1. Swaak, A.J., et al., Incomplete lupus erythematosus: results of a multicentre study under the supervision of the EULAR Standing Committee on International Clinical Studies Including Therapeutic Trials (ESCISIT). Rheumatology (Oxford) 2001; 40(1):89-94.

2. Graham RR, Ortmann W, Rodine P, et al. Specific combinations of HLA-DR2 and DR3 class-II haplotypes contribute graded risk for disease susceptibility and autoantibodies in human SLE. European J of Human Genetics 2007; 15:823-30

3. Olerup O, Zetterquist H. HLA-DR typing by PCR amplification with sequence-specific primers (PCR-SSP) in 2 hours: an alternative to serological DR typing in clinical practice including donor-recipient matching in cadaveric transplantation. Tissue Antigens1992;39(5):225-35

Disclosure of Interest None Declared