In addition to well-established Perrault syndrome genes involved in mitochondrial function, recent studies have described causative variants in non-mitochondrial genes including HSD17B4, GGPS1 and PEX6 in patients presenting with clinical features overlapping with Perrault syndrome (Fig. 7) (Tucker et al. 2020). The gene discussed is GGPS1; the disease is Perrault syndrome.