Monarch Disease Ontology identifier MONDO_0012301 (mitochondrial DNA depletion syndrome, myopathic form) is a rare mitochondrial DNA depletion syndrome characterized by muscle weakness, and progressive, generalized hypotonia due to depletion of mtDNA in skeletal muscles. Clinical progression ranges from rapid and early fatal course due to respiratory failure, to slowly progressive myopathy over the course of childhood or even early adulthood. Also known as: mitochondrial DNA depletion syndrome type 2, mtDNA depletion syndrome, myopathic form.