Mitochondrial Trifunctional Protein (TFP) is a multienzyme complex of the beta-oxidation cycle. TFP deficiency is a clinically heterogeneous disorder with phenotypes of different severity. The spectrum of diseases range from severe neonatal/infantile cardiomyopathy and early death to mild chronic progressive sensorimotor poly-neuropathy with episodic rhabdomyolysis. Human TFP is an octomer composed of four alpha-subunits and four beta-subunits. Mutations in either subunits may result in general TFP deficiency with reduced activity of all enzymes.