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.