The median value of serum GDF-15 levels (interquartile range) in patients with PMM was 1498 pg/mL (916–1856), 618 pg/mL (440–815) in patients with CFS, and 814 pg/mL (518-948) in patients with fatigue due to a non-mitochondrial disorder. Here, GDF15 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.