A novel Twinkle gene mutation in autosomal dominant progressive external ophthalmoplegia.

Autosomal dominant progressive external ophthalmoplegia is a common neurological presentation of mitochondrial disease and is characterised by multiple deletions of mitochondrial DNA in muscle. We describe a family with autosomal dominant progressive external ophthalmoplegia caused by a novel heterozygous A to C transversion at nucleotide 956 of the Twinkle gene. The deltoid muscle biopsy of the index case revealed sparse respiratory deficient cells. Multiple mitochondrial DNA deletions were clearly evident in the index case by both long-range and real-time polymerase chain reaction assays but not by Southern blotting, highlighting the diagnostic difficulties associated with characterising patients with multiple mitochondrial DNA deletions.