幼年型僵直性脊椎炎是一種表現周邊、薦髂關節發炎，以及接骨點炎之疾病；其表現與成人僵直性脊椎炎不同。雖然，HLA-B27在兒童及成人的僵直性脊椎炎都佔有重要的角色，但是其在兒童方面僅有38%的低盛行率。這個在中軸骨疾病的不同面向，使得青少年過度至成人的照護更顯困難。此外，幼年型僵直性脊椎炎也無法納入國際風濕病組織對於兒童特發性關節炎的其中一個次分類中。然而，薦骨關節炎是兒童特發性關節炎的一個不良預後因子，並且對於傳統疾病修飾抗風濕藥物療效不佳。生物製劑已被建議為非類固醇抗發炎藥物之後的第二線用藥。基於以上的情況，進一步的更新分類條件應有助於及早診斷與治療。

Juvenile spondyloarthritis (SpA) has features of arthritis, sacroiliitis and enthesitis, and its presentation is different from adult SpA. Although HLA-B27 is a prominent marker both in juvenile and adult spondyloarthritis, the low prevalence is associated with juvenile spondyloarthritis. In addition, the spine and sacroiliac joint involvement is an unusual presentation in children and adolescents at diagnosis. The progression to axial skeletal disease would be a crucial point for adolescence transition to adult care. Furthermore, SpA could not be defined well in the International League of Association for Rheumatology (ILAR) classification system for juvenile idiopathic arthritis. The different diagnostic criterion from adult SpA is also a challenge. These review summarized the clinical features, pathogenesis, treatment and outcomes of juvenile SpA, and emphasis on sacroiliitis. Sacroiliitis is a poor prognostic factor of juvenile idiopathic arthritis, and the response to conventional DMARDs is poor. Biological DMARDs are suggested for second line therapy after NSAIDs. Among these situations, the advanced classification should be renewed for early diagnosis and treatment.