A Rare Presentation of a 12-Year-Old With Systemic Infantile Hyalinosis: A Case Report and Review of the Literature.

This case report presents the clinical manifestation and diagnostic testing of a 12-year-old male diagnosed with systemic infantile hyalinosis (SIH) at the Maternity and Children Hospital in Madinah in 2012. The patient presented with typical SIH symptoms, including painful joint contractures, hyperpigmented knuckles, gingival hypertrophy, subcutaneous nodules, and recurrent infections. Whole exome sequencing (WES) analysis identified a homozygous mutation in the ANTXR2 gene, which is a deletion in exon 13 (c.1074delT; p.A359HfsX50), confirming the diagnosis. Notably, this patient's survival beyond the typical age expectancy of SIH, which is usually within the first few years of life, challenges the usual prognosis associated with this disease. This case emphasizes the importance of early diagnosis through clinical suspicion confirmed by genetic analysis and highlights the variability in disease presentation and prognosis.