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lipid myopathies
Saturday 4 February 2006
Abnormalities of the carnitine transport system or deficiencies of the mitochondrial dehydrogenase enzyme systems can lead to the accumulation of lipid droplets within muscle (lipid myopathies).
To undergo β-oxidation, cytoplasmic fatty acyl coenzyme A (acyl-CoA) esters are:
(1) transesterified with carnitine through the action of an outer membrane carnitine palmitoyltransferase (CPT I)
(2) transported across the inner mitochondrial membrane
(3) re-esterified to acyl-CoA esters by an inner membrane mitochondrial CPT (CPT II)
(4) catabolized to acetyl-CoA units by the acyl-CoA dehydrogenases.
In different patients with lipid myopathy, the defect may involve carnitine, acyl-CoA dehydrogenase, or CPT enzymes.
Morphology
In all of these lipid myopathies, the principal morphologic characteristic is accumulation of lipid within myocytes.
The myofibrils are separated by vacuoles that stain with oil red O or Sudan black and have the typical appearance of lipid by electron microscopy.
The vacuoles occur predominantly in type 1 fibers, and they are dispersed diffusely throughout the fiber.
See also
Myopathies