[Advances in genetic research on Non-syndromic congenital joint synostosis]

Congenital joint synostosis (CJS) is a functional impairment resulting from failure in joint morphogenesis during embryonic development. Clinically, it may be classified as syndromic (sCJS) and non-syndromic (nsCJS) disorders. Common sCJS include chromosomal disorders such as Klinefelter syndrome and single-gene disorders like Apert/Pfeiffer/Crouzon syndromes, Holt-Oram syndrome, Ehlers-Danlos syndrome, and Radial-ulnar synostosis with thrombocytopenia, presenting with multiple system/organ anomalies. By contrast, nsCJS manifest with only joint abnormalities, affecting one or multiple joints. This review has focused on human nsCJS and its genetic etiology. To date, variants in seven genes (NOG, GDF5, FGF9, GDF6, FGF16, SMAD6, and MECOM) have been identified as causative factors for nsCJS. This review has focused on such genes and provided a comprehensive review for the clinical phenotypes, genetic patterns, common variants, and underlying mechanisms associated with nsCJS based on a literature review. In addition, it has also analyzed other candidate genes for nsCJS within the context of relevant signaling pathways involved in joint morphogenesis.