GDF15 and systemic lupus erythematosus: One emerging marker of mitochondrial dysfunction and muscle damage is growth differentiation factor 15 (GDF-15), a mitomyokine (e.g. a myokine released by muscle cells, as well as a mitokine; a marker of mitochondrial stress), suggested as a promising biomarker in several autoimmune and inflammatory diseases such as diabetes mellitus type 1, anti-phospholipid syndrome and even systemic lupus erythematosus [4–6].