Much of the body's carnitine is present in skeletal muscle, where it is involved in transmembrane transfer of long-chain fatty acids into mitochondria. The fatty acids undergo beta-oxidation within the mitochondria in order to generate energy for muscle contraction. A primary carnitine disorder affecting muscle results in a myopathy.
Skeletal muscle involvement in a primary carnitine disorder may:
(1) be isolated to skeletal muscle
(2) involve both skeletal and cardiac muscle
(3) be part of aystemic disorder
Inheritance: autosomal recessive
Clinical features of myopathy associated with a primary carnitine disorder:
(1) proximal muscle weakness
(2) exercise intolerance
(3) myalgia
Finding
Disorder with Carnitine Deficiency
Carnitine Palmityl-transferase Deficiency
serum CK
often normal
elevated from rhabdomyo-lysis during fasting or strenuous exercise
muscle carnitine levels
decreased
normal
skeletal muscle biopsy
accumulation of fatty acids and triglycerides
minimal or no lipid accumulation
Mitochondria may be increased in number and/or massively enlarged on ultrastructural studies.
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