Carnitine Deficiency
A teenage boy was brought to a hospital as he complaints that he used to get too tired when asked to participate in the marching team. The doctor found muscle weakness in the boy’s arms and legs. From the muscle biopsy, the lab pathologist found greatly elevated amount of triglycerides esterified with primary long chain fatty acid. They also fund significant presence of lipid vacuoles in the muscle biopsy. What causes these symptoms?
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Carnitine deficiency is one of a group of metabolic muscle diseases that interferes with the processing of food (in this case, fats) for energy production. Carnitine deficiency may occur in response to a genetic mutation (gene defect) in the protein responsible for bringing carnitine into the cell (primary carnitine deficiency), or it may occur secondary to other metabolic diseases (secondary carnitine deficiency). The disease has its onset from infancy to early adulthood and is slowly progressive.
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Causes
The metabolic diseases of muscle are caused by genetic defects that interfere with chemical reactions involved in drawing energy from food.
Normally, fuel molecules derived from food must be further broken down inside each cell before they can be used by the cells’ mitochondria (or "engines") to make energy. Metabolic muscle diseases are caused by problems in the way certain fuel molecules are processed before they enter the mitochondria, or by the inability to get fuel molecules into mitochondria. Carnitine deficiency is caused by lack of a small, naturally occurring molecule that’s not an enzyme but is involved in metabolism. |
Enzymes are special types of proteins that act like little machines on a microscopic assembly line, each performing a different function to break down food molecules into fuel. When one of the enzymes in the line is defective, the process goes more slowly or shuts down entirely.
Our bodies use carbohydrates (starches and sugars), fats and protein for fuel. Defects in the cells’ carbohydrate- and fat-processing pathways usually lead to weakness in the voluntary muscles, but also may affect the heart, kidneys or liver. Although defects in protein-processing pathways can occur as well, these usually lead to different kinds of disorders that affect other organs
Our bodies use carbohydrates (starches and sugars), fats and protein for fuel. Defects in the cells’ carbohydrate- and fat-processing pathways usually lead to weakness in the voluntary muscles, but also may affect the heart, kidneys or liver. Although defects in protein-processing pathways can occur as well, these usually lead to different kinds of disorders that affect other organs