Juvenile spondyloarthritis (jSpA) represents a spectrum of inflammatory arthritis with strong HLA-B27 association and involvement of enthesis and/or axial skeleton that appears in children and young adults. ILAR classification criteria for enthesitis related arthritis subtype of juvenile idiopathic arthritis, which is undifferentiated form of jSpA, includes arthritis, enthesitis, presence of sacroiliac joint tenderness, inflammatory lumbosacral pain, HLA-B27 positivity, positive family history and acute anterior uveitis.

We present a case of 16 years old girl diagnosed with juvenile spondyloarthritis that first presented with recurrent monthly swelling of index finger at the age of 14. Symptoms progressed to low back pain in the morning which partly declined with activity. Additionally, her right knee was swollen and painful. She was examined on multiple occasions by pediatric orthopedic surgeon and in pediatric emergency department before seeing a pediatric rheumatologist. The first examination revealed sacroiliac joint tenderness with positive FABER test and abnormal modified Schober test. Family history was negative for rheumatic diseases and there were no signs of uveitis nor enthesitis, with ANA, RF and extensive laboratory workup being either negative or within reference range. However, HLA-B27 turned positive and MRI showed right sacroiliitis. NSAID was prescribed but symptoms nevertheless persisted. Thus, after the exclusion of TBC with quantiferon test, intraarticular corticosteroid injection was applied to the right knee and oral corticosteroid was introduced as bridging therapy. Subsequently, according to ACR guidelines, a therapy with TNF-alpha inhibitor, adalimumab, was initiated. Within a month, a substantial reduction of the low back pain was noted, with a decrease in juvenile spondyloarthritis disease activity score (jSpADA).

Low back pain often begins in childhood, with the prevalence in adolescence being similar to that in adulthood. Among many possible causes, inflammatory etiology should be thoroughly considered due to irreversible damage if not treated adequately. Therefore, children and adolescents complaining of a back pain, especially in the presence of other signs of arthritis, should be referred to pediatric rheumatologist for a further work-up and treatment.