X-linked creatine transporter deficiency presenting as a mitochondrial disorder.

X-linked creatine transporter defect is caused by mutations in SLC6A8 at Xq28, which encodes the sodium-dependent creatine transporter. Reduction in creatine uptake results in elevated urine creatine and CSF creatine deficiency, which can be detected on magnetic resonance spectroscopy. We report a patient who was initially suspected of having a mitochondrial disorder but was later found to have a creatine transporter defect. The abnormal laboratory study results seen in this patient suggesting a mitochondrial cytopathy could be due to excess mitochondrial stress as well as the mitochondrial inclusion bodies. This report looks at the mitochondrial presentation of the creatine transporter deficiency.