Clinicogenetic lessons from 370 patients with autosomal recessive limb‐girdle muscular dystrophy

Abstract

Limb‐girdle muscular dystrophies (LGMD) are a group of genetically heterogeneous disorders characterized by predominantly proximal muscle weakness. We aimed to characterize epidemiological, clinical and molecular data of patients with autosomal recessive LGMD2/LGMD‐R in Brazil. A multicenter historical cohort study was performed at 13 centers, in which index cases and their affected relatives data from consecutive families with genetic or pathological diagnosis of LGMD2/LGMD‐R were reviewed from July 2017 to August 2018. Survival curves to major handicap for LGMD2A/LGMD‐R1‐calpain3‐related, LGMD2B/LGMD‐R2‐dysferlin‐related and sarcoglycanopathies were built and progressions according to sex and genotype were estimated. In 370 patients (305 families) with LGMD2/LGMD‐R, most frequent subtypes were LGMD2A/LGMD‐R1‐calpain3‐related and LGMD2B/LGMD‐R2‐dysferlin‐related, each representing around 30% of families. Sarcoglycanopathies were the most frequent childhood‐onset subtype, representing 21% of families. Five percent of families had LGMD2G/LGMD‐R7‐telethonin‐related, an ultra‐rare subtype worldwide. Females with LGMD2B/LGMD‐R2‐dysferlin‐related had less severe progression to handicap than males and LGMD2A/LGMD‐R1‐calpain3‐related patients with truncating variants had earlier disease onset and more severe progression to handicap than patients without truncating variants. We have provided paramount epidemiological data of LGMD2/LGMD‐R in Brazil that might help on differential diagnosis, better patient care and guiding future collaborative clinical trials and natural history studies in the field.