Various mitochondrial abnormalities, such as the presence of mitochondrial inclusions and the accumulation of enlarged bizarre mitochondria, were previously reported in muscle tissues from patients with a presumptive and/or a confirmed diagnosis of ZSD [15, 34–37], in patients with PEX16 and PEX12 mutations [15] and in a mouse model carrying a PEX13 deletion, which led to aberrant accumulation of mitochondria in brain tissue [13]. The gene discussed is PEX13; the disease is peroxisome biogenesis disorder.