Mitochondrial Dysfunction Contributes to Ehlers-Danlos Syndrome - A Patient Presentation

A female patient with substantial history and physical findings of Ehlers-Danlos syndrome by systematic evaluation had a variant in the gene encoding the sixth subunit of mitochondrial ATP synthetase gene that produced a change from glycine to aspartic acid at position 132 of the MT-ATP6 protein (MT-ATP6 m.8921G>A, p.Gly132Asp). The mutation was heteroplasmic, affecting 32% of the mitochondria in blood leucocytes, was qualified as a pathogenic variant because of its significant molecular change, but was not detected in the maternal blood sample as might be expected for its low degree of heteroplasmy. The patient was shown to have typical findings of Ehlers-Danlos syndrome by comparison of 48 history and physical findings in her and a peer group of 32 teenage females with that diagnosis. None of the classical neurosensory or developmental symptoms of mitochondrial disease were present in mother or daughter, but the patient had symptoms, metabolite alterations during rest or exercise, and muscle biopsy changes that suggested mild mitochondrial dysfunction. She also had heterozygous variants of uncertain significance in the nuclear PLOD1, FLNA, and ATP2A genes by concomitant whole exome sequencing that could also contribute to her arthritis-adrenaline disorder. Mitochondrial dysfunction is proposed to influence neuromuscular components of connective tissue, acting through an articulo-autonomic dysplasia cycle to cause the typical joint-skin laxity and dysautonomia of Ehlers-Danlos syndrome.