Dear Shubankar,

HLA B27 positivity is seen in 2-10% of Indian population based on different studies. It is a genetic marker and does not change on repeated testing. So there is no logic in repeating the test again and again. Yes, there is some discordance between the test results between flow cytometry Vs PCR but that is a different matter altogether.

Treatment and labels are 2 different aspects. A documented polyarthritis of 6 months duration with definite evidence of inflammation needs to be treated with DMARDs, almost similar to the way you would a patient of RA, irrespective of the final label you would bestow upon the individual. 

Prevalence of adult RA in India itself is about 0.5% while JIA is closer to 1: 1000 to 1: 2000. Since HLA B27 can be as high as upto 10%, it means for every 1 child with JIA, there are likely to be 100-200 normal children without JIA who would be HLA B27 positive. So, this test has no diagnostic significance unless you have reasonable clinical pre test probability of the child having oligoarticular JIA or enthesitis related JIA or Juvenile SpA. In such a situation, this test will increase your post test probability. 

Hope this helps

regards

Thank you sir for your elaborate explanations.

the first point is that one should base diagnosis on clinical picture and not on investigations. Autoantibodies are only a guide, not the diagnosis. at an early stage of your career don't fall in habit of investigations first.

polyarthritis i assume is symmetrical and affecting small joints of UL in this patient would be a RA distribution. Your work up should include RA D/D and investigations. remember RF,ANA have no diagnostic value in a pt of JIA.

HLA B27 is likely to be incidental. However i would look for present or past psoriasis in relatives of the patient. also get a x-ray/mri of the sacriliac joints for better evaluation.

Dear Dr Shubankar,

It is the clinical pattern in JIA, which helps in further subclassification and managing these patients. Criteria mentioned in textbooks are meant for classification and not for a diagnosis. As already elucidated by Dr Shankar Subramanian, there should be a reasonable pretest probability for doing HLA B27.

First coming to the issue of polyarthritis, it is important to know whether there is any associated systemic symptoms. Severe excruciating pain is usually not a feature of inflammatory arthritis. If this is an inflammatory arthritis and no other systemic features, based on clinical pattern we can differentiate to some extent:

       -Symmetrical involving small and large joints- RF positive poly JIA (usually   seen in older children)

       -Asymmetrical involving small and large- RF neg poly JIA/ psoriatic arthritis.

However, having said that, diagnosis and treatment are two different issues. 6 months history of inflammatory polyarthritis would definitely warrant a DMARD, preferrably methotrexate.

Dear Dr. Shubhankar,

ERA appears infrequently below 5 years, and it is usually associated with: male gender, oligoarticular involvement, mostly asymmetrical, over lower limbs large joints, enthesitis, sacroiliac pain or lumbar spine limitation (this may be a late finding), dactylitis, elevation of APRs and HLA B27 positivity. Your patient does not seem to present any of these except for the HLA allele.

Polyarticular JIA, especially the Rheumatoid Factor negative type, is commonly seen during the early years of age, commonly involves large and small joints of both upper and lower limbs, upper spine (cervical), while lower spine and entheses are usually spared. Your patient resembles this latter picture. However, the HLAB27 positivity prevents us from classifying your patient as Polyarthritis, while he does not meet enough criteria for ERA (I assume his family history was negative for spondyloarthropathy or other B27-related diseases).Naturally, should find a repeatedly positive Rheumatoid Factor your patient is clearly a RF-positive Polyarthritis.

Today your patient seems to fit under the "Undifferentiated Arthritis" type of the ILAR criteria. Nevertheless, given his B27 positivity (and thus an increased risk of developing lower spine invovement later on) I would follow him closely with clinical/imaging techniques to eventually detect sacroiliac impact early.

Answering your question: HLA-B27 frequency in Polyarthritis seems to be similar to the one in the general population: 3-10 % (Thompson et al. Juvenile idiopathic arthritis classified by the ILAR criteria: HLA associations in UK patients. Rheumatology 200241:1183-1189). The frequency in the patient´s particular ethnic background could give you a better estimation.

Best wishes,

Thank you all for your superb response. I will closely follow the patient to detect any new sacroiliac involvement. 

Dear Dr. Shubhankar,

As my colleagues already mentioned above I would agree with the opinion that the clinical presentation of your patient fits better with the polyarticular JIA rather than ERA. Lack of sacroiliac joints involvement and enthesitis, in spite of positive HLA-B27, does not give us the diagnosis of ERA. In European population the incidence of HLA-B27 is up to 20% in healthy population, as well as in JIA patients that have not the features of ERA. There are no data about the family history of your patient, which would be also informative. There are no data of other laboratory findings, such as markers of inflamation, RF, ANA. X-ray or even better MRI of SI joints should be done in the future follow up, as well as the US of inflamed periferal joints. Ophtalmological examinations should be performed at least 2-3 times a year for uveitis.

Treatment depends on the type of JIA, which for your patient with polyarticular JIA would certainly be methotrexate, while for ERA  better option is salazopyrine.

Best wishes

Lana Tambić Bukovac

What is his blood work eg CBC PS ,  Inflammatory markers? Did you exclude other causes of chronic arthritis? Because sever pain is not part of JIA.

IF you ruled out other causes of chronic arthritis, I think your patient is more of poly JIA. AND you should manage him as per ACR guidelines