A novel CAPN3 mutation in late-onset limb-girdle muscular dystrophy with early respiratory insufficiency.

We describe a 70 year-old independently ambulatory man with a 10-year history of progressive axial and limb-girdle weakness, hyperCKemia, and a 5-year history of dyspnea requiring nocturnal ventilatory support due to a known c.1309C>T (p.Arg437Cys) variant and a novel in-frame deletion of exons 17-19 in the calpain-3 encoding gene (CAPN3). Pulmonary function tests revealed neuromuscular respiratory weakness. Biceps femoris biopsy showed chronic myopathic changes, numerous lobulated fibers, and reduced calpain-3 immunoreactivity. Muscle immunoblot showed markedly reduced calpain-3 expression. Respiratory insufficiency is uncommon in autosomal recessive calpainopathy, and generally develops in the advanced stages of the disease when individuals become wheelchair-dependent. Our patient broadens the phenotypic spectrum of recessive calpainopathy to include early respiratory insufficiency and also further expands its molecular spectrum.