From OMIM
The mitochondrial trifunctional protein, composed of 4 alpha and 4 beta subunits, catalyzes 3 steps in mitochondrial beta-oxidation of fatty acids: long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD), long-chain enoyl-CoA hydratase, and long-chain thiolase activities. Trifunctional protein deficiency is characterized by decreased activity of all 3 enzymes. Clinically, classic trifunctional protein deficiency can be classified into 3 main clinical phenotypes: neonatal onset of a severe, lethal condition resulting in sudden unexplained infant death (SIDS; 272120), infantile onset of a hepatic Reye-like syndrome, and late-adolescent onset of primarily a skeletal myopathy (Spiekerkoetter et al., 2003). Some patients with MTP deficiency show a protracted progressive course associated with myopathy, recurrent rhabdomyolysis, and sensorimotor axonal neuropathy. These patients tend to survive into adolescence and adulthood (den Boer et al., 2003). Genetic Heterogeneity of Mitochondrial Trifunctional Protein Deficiency See also MTPD2 (620300), caused by mutation in the HADHB gene, the beta subunit of the mitochondrial trifunctional protein.  http://www.omim.org/entry/609015

From MedlinePlus Genetics
Mitochondrial trifunctional protein deficiency is a rare condition that prevents the body from converting certain fats to energy, particularly during periods without food (fasting).

Signs and symptoms of mitochondrial trifunctional protein deficiency may begin during infancy or later in life. Features that occur during infancy include feeding difficulties, lack of energy (lethargy), low blood glucose (hypoglycemia), weak muscle tone (hypotonia), and liver problems. Infants with this disorder are also at high risk for serious heart problems, breathing difficulties, coma, and sudden death. Signs and symptoms of mitochondrial trifunctional protein deficiency that may begin after infancy include hypotonia, muscle pain, a breakdown of muscle tissue, and a loss of sensation in the extremities (peripheral neuropathy).

Problems related to mitochondrial trifunctional protein deficiency can be triggered by periods of fasting or by illnesses such as viral infections. This disorder is sometimes mistaken for Reye syndrome, a severe disorder that may develop in children while they appear to be recovering from viral infections such as chicken pox or flu. Most cases of Reye syndrome are associated with the use of aspirin during these viral infections.  https://medlineplus.gov/genetics/condition/mitochondrial-trifunctional-protein-deficiency