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There has
been considerable controversy regarding the role of L-carnitine
(Carnitor®,
Sigma-Tau Pharmaceuticals, Inc.) and its value as a supplemental
therapy in fat oxidation disorders. Currently, there is concern
that it could actually be harmful with VLCAD Deficiency. There is
actually no concrete evidence for this concern; in fact, there has
been much experience that indicates that there is no harmful aspect
of L-carnitine in patients with VLCAD Deficiency. It is now known
that VLCAD Deficiency can present in three very different ways.
These phenotypes should be recognized when discussing the question
of carnitine supplementation in this inherited disorder.
- Some children with VLCAD present identically to
MCAD Deficiency-Hypoglycemia (VLCAD-H).
- Some present as recurrent rhabdomyolysis (muscle
breakdown like adult onset CPTII Deficiency). These patients are
usually young adults or teenagers (VLCAD-M).
- Many children present as the cardiomyopathic form
and have often died in the first year of life (VLCAD-C). They
also have problems with blood sugar and muscle is also involved.
VLCAD-H seems
to only involve liver metabolism. VLCAD-M involves skeletal muscle
only, whereas VLCAD-C involves heart, muscle and liver.
All have
been treated with L-carnitine supplement and increased concentrations
of medium-chain triglyceride (MCT) containing formulas or diets.
In our experience, there has not been any untoward effect of L-carnitine,
including heart rhythm disturbances, in any of these patients even
during acute illnesses during which intravenous carnitine was administered
to patients with the cardiomyopathic form of the disease.
The reason
we use L-carnitine in VLCAD Deficiency is to maintain a reasonably
normal ratio of Free Co-enzyme A to esterified Coenzyme A to facilitate
mitochondrial metabolism during fat mobilization due to fasting
or unexpected illness.
For further
discussion of the direct experience with long-chain fat oxidation
disorders, including VLCAD, please feel free to contact us. For
those who have had a different direct experience with L-carnitine
and a patient, we would be interested in the details.
Dr. Charles
R. Roe
Dr.
Alfred Slonim
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