Inter- and intra-familial phenotypic variability of autosomal dominant collagen VI related disorder.

Background: Collagen VI-related disorder (COL6-RD) is an inherited neuromuscular disease characterized by a broad spectrum of phenotypes.

Patients and methods: Eight families with autosomal dominant COL6-RD were recruited. Clinical manifestations, laboratory findings, electrophysiological results, molecular analyses, and pathological outcomes of eight index patients and their affected family members were systematically collected and reviewed.

Results: Pathogenic variants were identified in four families in the COL6A1 gene, one family in the COL6A2 gene, and three families in the COL6A3 gene. Among the index patients, three were classified as moderate progressive Ullrich congenital muscular dystrophy (UCMD), four exhibited mild UCMD or Bethlem myopathy, and one was diagnosed with Bethlem myopathy. The phenotypic presentation was relatively consistent within four families. However, intra-familial phenotypic variability was observed in four families, encompassing a wide range of onset ages, patterns and degrees of muscle weakness, rates of contracture progression, severity of skin changes, and age at loss of ambulation.

Conclusion: Inter- and intra-familial phenotypic variability is prevalent in autosomal dominant COL6-RDs. When predicting the clinical course and severity for patients, it is crucial to integrate a comprehensive set of information, including mutation sites and types, family history, and early presenting features.