combined oxidative phosphorylation deficiency 33 (EFO_0009159, an Experimental Factor Ontology term) (COXPD33) is an autosomal recessive multisystem disorder resulting from a defect in mitochondrial energy metabolism. The phenotype is highly variable, ranging from death in infancy to adult-onset progressive external ophthalmoplegia (PEO) and myopathy. A common finding is cardiomyopathy and increased serum lactate (summary by Feichtinger et al., 2017). Also known as: COXPD33.