Merosin-deficient Congenital Muscular Dystrophy Type 1a: Detection of Variants in Vietnamese Patients

Merosin-deficient congenital muscular dystrophy type 1A (MDC1A), also known as laminin-α2 chain-deficient congenital muscular dystrophy (-MD), is an autosomal recessive disease caused by biallelic variants in the gene. In MDC1A, laminin- α2 chain expression is absent or significantly reduced, leading to some early-onset clinical symptoms including severe hypotonia, muscle weakness, skeletal deformity, non-ambulation, and respiratory insufficiency. Six patients from five unrelated Vietnamese families presenting with congenital muscular dystrophy were investigated. Targeted sequencing was performed in the five probands. Sanger sequencing was carried out in their families. Multiplex ligation-dependent probe amplification was performed in one family to examine an exon deletion. Seven variants of the (NM_000426) gene were identified and classified as pathogenic/likely pathogenic variants using American College of Medical Genetics and Genomics criteria. Two of these variants were not reported in the literature, including c.7156-5_7157delinsT and c.8974_8975insTGAT. Sanger sequencing indicated their parents as carriers. The mothers of family 4 and family 5 were pregnant and a prenatal testing was performed. The results showed that the fetus of the family 4 only carries c.4717 + 5G>A in the heterozygous form, while the fetus of the family 5 carries compound heterozygous variants, including a deletion of exon 3 and c.4644C>A. Our findings not only identified the underlying genetic etiology for the patients, but also provided genetic counseling for the parents whenever they have an offspring.