Isolated ATP synthase deficiency

Isolated ATP synthase deficiency (also known as mitochondrial complex V deficiency or isolated mitochondrial ATP synthase deficiency) is a rare inherited disorder of mitochondrial energy metabolism. ATP synthase (complex V) is the final enzyme in the mitochondrial oxidative phosphorylation chain, responsible for generating the majority of cellular ATP — the primary energy currency of the cell. When this enzyme is deficient, cells cannot produce adequate energy, leading to dysfunction predominantly in tissues with high energy demands such as the brain, heart, and skeletal muscles. Clinical features are highly variable but commonly include neonatal-onset lactic acidosis, hypertrophic cardiomyopathy, muscular hypotonia, psychomotor delay, and failure to thrive. Some patients present with 3-methylglutaconic aciduria. Neurological involvement may include encephalopathy, developmental regression, and seizures. The severity ranges from fatal neonatal presentations to milder forms with longer survival. Multi-organ involvement is common, and affected individuals may also develop hepatic dysfunction and peripheral neuropathy. The condition can be caused by mutations in several nuclear genes encoding structural subunits or assembly factors of ATP synthase, including ATP5F1A, ATP5F1D, ATP5F1E, ATP5MC3 (ATP5G3), ATPAF2, and TMEM70 — with TMEM70 mutations being the most frequently identified cause, particularly in the Roma population. Mitochondrial DNA mutations in MT-ATP6 and MT-ATP8 can also cause this condition. Treatment is primarily supportive and symptomatic, focusing on management of metabolic crises, cardiac complications, and nutritional support. There is no curative therapy currently available, though avoidance of metabolic stressors and supplementation with cofactors such as coenzyme Q10 and riboflavin may be attempted on an empirical basis.

Common questions about Isolated ATP synthase deficiency