A rare homozygous CAPN3 variant with distinct clinical features in unrelated families of Iraqi Jewish descent

CAPN3 encodes a calcium-activated skeletal muscle-specific protease. Pathogenic variants in CAPN3 are associated with autosomal recessive and dominant limb-girdle muscular dystrophy. We report on three children and one adult from four unrelated Iraqi Jewish families, who harbor the same homozygous variant in CAPN3, p.Gln123Lys. Patients shared recognizable features of toe-walking and elevated creatine phosphokinase since childhood. The variant affects a conserved protein domain common to the calpain super family and likely represents a founder mutation in individuals of Iraqi Jewish ancestry. Our findings have potential implications on screening in relevant populations, allowing for more prompt diagnoses and future therapies.