MT-ATP6 and NARP syndrome: The presentation and severity of these are usually dependent on the level of mutant mtDNA (heteroplasmic load) in different tissue types.3 Recently, the clinical spectrum of mitochondrial ATP synthase disorders has expanded further to include axonal Charcot-Marie-Tooth disease,4 late-onset hereditary spastic paraplegia-like disorder,5 and episodic weakness.6 The majority of MT-ATP6 mutations are missense; only 3 truncating mutations are reported, all of which presented with ataxia, developmental delay, or NARP.7, –, 9