ABSTRACT
BACKGROUND AND PURPOSE: The aim was to determine the genetic background of unknown muscular dystrophy in five French families. METHODS: Twelve patients with limb girdle muscular dystrophy or distal myopathy were clinically evaluated. Gene mutations were identified using targeted exon sequencing and mutated DNAJB6 was tested in vitro. RESULTS: Five patients presented with distal lower limb weakness whilst others had proximal presentation with a variable rate of progression starting at the mean age of 38.5 years. Two novel mutations (c.284A>T, p.Asn95Ile, two families; and c.293_295delATG, p.Asp98del, one family) as well as the previously reported c.279C>G (p.Phe93Leu, two families) mutation in DNAJB6 were identified. All showed a reduced capacity to prevent protein aggregation. CONCLUSIONS: The mutational and phenotypical spectrum of DNAJB6-caused muscle disease is larger than previously reported, including also dysphagia. The originally reported c.279C>G (p.Phe93Leu) mutation is now identified in four different populations and appears to be a mutational hotspot. Our report confirms that some DNAJB6 mutations cause distal-onset myopathy and hence DNAJB6 defects should be considered broadly in dominant muscular dystrophy families.