P035 Important role of HLA laboratory in the diagnosis of HLA associated diseases

A 43 years old female patient was introduced to our polyclinic and the treating physician referred her to our HLA-lab for HLA-B27 typing. According to the ordering physician the patient is suffering from back pain, stiffness in the morning, degenerative changes, facet Arthropathy and her hip was also affected, hence we were suspicious that the patient was suffering from ankylosing spondylitis. The blood pressure was normal, BMI 29, WBC 6,849/L, HB 146 g/dl, Glc 5.5 mmol/L, PTH 56.6 ng/L, anti gliedin 3.88 mg/L, CRP 3.46 mg/L. According to published studies HLA-B27 is present in 85% of patients with ankylosing spondylitis. This means that HLA-B27 positive individuals are approximately 85 times at more risk to develop ankylosing spondylitis compared to the general population. However, in this case our HLA-typing, which was performed for HLA-Class I by using SSO for low/intermediate resolution, showed a negative result for HLA-B27. The negative HLA-typing results for HLA-B27 in this female patient do not totally exclude the presence of ankylosing spondylitis because 15% of affected patients do not carry this HLA allele. However, the absence of HLA-B27 in this patient makes the diagnosis of ankylosing spondylitis unlikely. This interpretation is supported by the fact, that Ankylosing spondylitis predominantly affects male patients and not females in the age  > 30 years old. In addition, the described clinical symptoms could be caused by many other various diseases. At our lab we usually performed the testing of all HLA class I alleles even when only single allele requested. In this case we have observed that the patient has beside HLA-B27 HLA-B51 also, which is very strongly associated with Behcet’s disease. Behcet’s disease has similar clinical symptoms to ankylosis spondylitis. Our positive results for HLA-B51 directed the treating physicians to perform further investigations to confirm Behcet’s disease instead of ankylosing spondylitis. The presented case highlights the important role of HLA laboratory in the diagnosis of HLA associated diseases.