Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort.

BACKGROUND LAMA2-related muscular dystrophy including LAMA2-related congenital muscular dystrophy (LAMA2-CMD) and autosomal recessive limb-girdle muscular dystrophy-23 (LGMDR23) is caused by LAMA2 pathogenic variants. We aimed to describe the natural history and establish genotype-phenotype correlations in a large cohort of Chinese patients with LAMA2-related muscular dystrophy. METHODS Clinical and genetic data of LAMA2-related muscular dystrophy patients enrolled from ten research centers between January 2003 and March 2021 were collected and analyzed. RESULTS One hundred and thirty patients (116 LAMA2-CMD and 14 LGMDR23) were included. LAMA2-CMD group had earlier onset than LGMDR23 group. Head control, independent sitting and ambulation were achieved in 76.3%, 92.6% and 18.4% of LAMA2-CMD patients at median ages of 6.0 months (range 2.0-36.0 months), 11.0 months (range 6.0-36.0 months), and 27.0 months (range 18.0-84.0 months), respectively. All LGMDR23 patients achieved independent ambulation at median age of 18.0 months (range 13.0-20.0 months). Motor regression in LAMA2-CMD mainly occurred concurrently with rapid progression of contractures during 6-9 years old. Twenty-four LAMA2-related muscular dystrophy patients died, mostly due to severe pneumonia. Seizures occurred in 35.7% of LGMDR23 and 9.5% of LAMA2-CMD patients. Forty-six novel and 97 known LAMA2 disease-causing variants were identified. The top three high-frequency disease-causing variants in Han Chinese patients were c.7147C > T (p.R2383*), exon 4 deletion, and c.5156_5159del (p.K1719Rfs*5). In LAMA2-CMD, splicing variants tended to be associated with a relatively mild phenotype. Nonsense variants were more frequent in LAMA2-CMD (56.9%, 66/116) than in LGMDR23 (21.4%, 3/14), while missense disease-causing variants were more frequent in LGMDR23 (71.4%, 10/14) than in LAMA2-CMD (12.9%, 15/116). Copy number variations were identified in 26.4% of survivors and 50.0% of nonsurvivors, suggesting that copy number variations were associated with lower rate of survival (p = 0.029). CONCLUSIONS This study provides better understandings of natural history and genotype-phenotype correlations in LAMA2-related muscular dystrophy, and supports therapeutic targets for future researches.