Expanded clinical and genetic characterization of autosomal recessive HMGCR-related muscular dystrophy

Autosomal recessive Limb-Girdle Muscular Dystrophy type R28 (LGMDR28; OMIM #620375) is one of the most recently identified subtypes of recessive LGMD. To date, 17 affected individuals from eight unrelated families have been reported to harbor biallelic variants in the HMGCR gene. Here, we report eleven individuals from six unrelated Middle Eastern families diagnosed with LGMDR28 and carrying homozygous variants in HMGCR. Our cohort recapitulated most of the previously described clinical features of the HMGCR-related phenotype. In addition, we also report a family with congenital onset of the condition as well as two affected individuals with liver failure. Through genome and exome sequencing, we identified three novel homozygous missense variants; c.2519G >A, p.(Arg840Gln), c.1784G >A, p.(Arg595His), and c.1783C>T, p.(Arg595Cys) and a homozygous in-frame deletion (c.1522_1524del, p.(Ser508del)) previously reported in compound heterozygous state with a second relevant variant and very recently as homozygous in an unrelated proband. This study consolidates the pathogenic role of HMGCR in LGMDR28 while expanding the phenotypic and mutations spectrum of LGMDR28.