A Novel Splice Site Variant in COL6A1 Causes Ullrich Congenital Muscular Dystrophy in a Consanguineous Malian Family.

Abstract

Background: Congenital muscular dystrophies (CMDs) are diverse early-onset conditions affecting skeletal muscle and connective tissue. This group includes collagen VI-related dystrophies such as Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy (BM), caused by mutations in the COL6A1, COL6A2 and COL6A3 genes. We report a consanguineous Malian family with three siblings affected by UCMD due to a novel homozygous splice site variant in the COL6A1 gene.

Methods: After obtaining consent, three affected siblings and their relatives underwent physical examinations by specialists and laboratory tests where possible. DNA was extracted from peripheral blood for genetic testing, including Whole Exome Sequencing (WES). Putative variants were confirmed through Sanger Sequencing and assessed for pathogenicity using in silico tools.

Results: The three siblings and their healthy parents, from a consanguineous marriage, presented with early-onset progressive muscle weakness, walking difficulty, proximal motor deficits, severe muscle atrophy, hypotonia, skeletal deformities, joint hyperlaxity, ankyloses at the elbows and knees, keloid scars and dental crowding. No cardiac involvement was detected and creatine kinase (CK) levels were normal. All had low serum calcium levels, treated with oral supplements. Needle myography indicated myopathic patterns. WES identified a novel splice site variant in the first intron of COL6A1 (c.98-1G>C), which segregated with the disease within the family. This variant is predicted to cause exon 2 skipping in COL6A1, with a high CADD score of 33 and Splice AI predicting it as deleterious.

Conclusion: We identified a novel COL6A1 variant in a consanguineous family, highlighting the need for further studies in larger African cohorts to enhance genetic epidemiology and prepare for future therapeutic research.