¹Bushra Yousef Abu Saleh, ¹Khulood Khawaja, ¹Vijay Kumar, ¹Ikram Shaalan

¹Sheikh Shakhbout Medical City

Background(s): Juvenile idiopathic arthritis (JIA) comprises various chronic inflammatory joint disorders in children, typically characterized by arthritis persisting for more than six weeks before the age of 16 years. Oligoarticular JIA, affecting fewer than five joints in the initial six months, is the most common subtype among pediatric patients. However, while extra-articular manifestations, including sacro-ileitis, are relatively rare, they present significant diagnostic and management challenges. Human leukocyte antigen (HLA) associations, notably HLA-B27, are well-established in JIA, particularly in aggressive arthritis like axial spondyloarthritis. In contrast, the role of HLA-B51, known for its extra-articular manifestations, remains less explored in pediatric arthritis cases.

Method(s): Chart review of the patient reporting her disease course and her MRI images. case report

Result(s): We present the case of a pediatric patient diagnosed with oligoarticular juvenile idiopathic arthritis initially but later identified as having an HLA-B51-positive status. The patient, a 3-year-old girl, presented with knee arthritis, for which she received a steroid injection followed by methotrexate therapy. Subsequent follow-up revealed her HLA-B51 positivity, suggesting a potential HLA-related arthritis. Approximately a year later, she developed non-specific back pain, eventually diagnosed by MRI contrast as unilateral sacro-ileitis, an unusual manifestation in pediatric patients. This case underscores the distinction between oligoarticular JIA and HLA-related arthritis, emphasizing the importance of genetic factors in pediatric rheumatology.

Conclusion(s): The occurrence of HLA-B51-associated unilateral sacro-ileitis in this pediatric patient highlights the complexity of JIA and its diverse presentations. While oligoarticular JIA is common in pediatric patients, the identification of HLA-B51 positivity underscores the potential familial genetic factors  giving the early manifestations of sacro-ileitis. This case emphasizes the need for careful consideration of genetic factors in pediatric rheumatology, as differentiating between various subtypes of JIA, including those associated with specific HLA alleles, is crucial for accurate diagnosis and management. Further research is warranted to elucidate the role of HLA-B51 in pediatric arthritis and its implications for clinical practice.