Childhood Juvenile idiopathic arthritis combined with Klinefelter syndrome: a case report and literature review.

Klinefelter syndrome (KS) is a chromosomal karyotype abnormality, most commonly presenting with the 47,XXY karyotype, and it has been associated with a variety of autoimmune diseases (AD). Juvenile idiopathic arthritis (JIA) is a chronic inflammatory disorder of unknown etiology that primarily affects the joints, with pathogenesis likely involving interactions among genetic predisposition, immune systems, and environmental exposure. Here we report the youngest known case of JIA complicated with KS to date, and the first pediatric case seen in China, who was hospitalized in the Pediatrics Department of Huizhou Central People's Hospital in February 2021. Clinical manifestations, physical signs, immunological indices, joint imaging findings, sex hormone levels, and chromosomal analysis were evaluated. Relevant literature was reviewed to explore potential mechanisms underlying the increased susceptibility of KS patients to autoimmune diseases. This predisposition may be related to X chromosome inactivation and sex hormone imbalance. Greater awareness of KS is warranted, and clinicians should recognize the elevated risk of autoimmune disorders in these patients. Chromosomal testing in young male children with autoimmune disorders is recommended.