Carnitine Palmitoyltransferas... Health Article

Diagnosis

The symptoms of CPT-I deficiency can be dramatic, but the rare nature of the disease means that some time may elapse while other more common diseases are ruled out. Definitive diagnosis of CPT-I deficiency is made by measuring the activity of the CPT enzyme in fibroblasts, leukocytes, or muscle tissue. Abnormal results on several blood tests are also typical of CPT-I deficiency, but the most important finding is hypoketotic hypoglycemia. Analysis of the CPT1 gene on chromosome 11 may be possible, but is not yet considered a diagnostic test.

CPT-II deficiency is somewhat more common than CPT-I deficiency. However, the milder symptoms of muscle CPT deficiency and their similarity to other diseases often leads to a wrong diagnosis (misdiagnosis). For example, the symptoms of CPT-II deficiency are sometimes initially diagnosed as fibromyalgia or chronic fatigue syndrome. Misdiagnosis is a special concern for people with muscle CPT-II deficiency, since the use of available preventive measures and treatment are then delayed.

Analysis of the CPT-II enzyme levels can confirm the diagnosis, but must be done carefully if performed on any tissue other than a muscle specimen. Direct testing of the CPT2 gene is available and is probably the easiest method (simple blood sample) of making the diagnosis. If genetic testing shows two mutated CPT2 genes, the diagnosis is confirmed. However, not all disease-causing mutations in the gene have been discovered, so demonstration of only one mutated CPT2 gene, or a completely negative test, does not exclude the diagnosis. In those individuals in whom genetic testing is not definitive, the combination of clinical symptoms and a laboratory finding of low levels of CPT-II enzyme activity should be enough to confirm the diagnosis.

Treatment and management

While CPT-I and CPT-II deficiency differ in their typical age of onset and in the severity of their symptoms, treatment of both conditions is similar. Attacks may be prevented by avoiding those situations that lead to them, as noted above. Someone undergoing surgery should discuss the possibility of alternative anesthetics with their doctor. Most people with CPT deficiency find it necessary to carry or wear some type of identifying information about their condition such as a Medic-Alert bracelet.

Those who find that they cannot avoid a situation known to be a trigger for them should try to supplement their diet with carbohydrates. Since medium-chain fatty acids to not require carnitine to enter the mitochondrion, use of a dietary supplement containing them results in significant improvement in people with CPT-I deficiency and also helps prevent attacks in most people with CPT-II deficiency. The use of carnitine supplements (vitamin B7) is also helpful for some individuals diagnosed with the deficiency.

Anyone diagnosed with CPT deficiency, or anyone concerned about a family history of CPT deficiency, should be offered genetic counseling to discuss the most up-to-date treatment and testing options available to them.

Prognosis

Children with CPT-I deficiency improve significantly with treatment. So far, however, all have had some lasting neurological problems, possibly caused by damage to the brain during their first attack. The outlook at this point for infants and children with liver and multi-organ CPT-II deficiency is still poor.

Once a person with muscle CPT-II deficiency is correctly diagnosed, the prognosis is good. While it is impossible for many patients to completely avoid attacks, most people with the condition eventually find the right mix of preventive measures and treatments. CPT-II deficiency then has much less of a harmful impact on their lives. A number of excellent sources of information are available for families affected by CPT deficiency. Any new treatments in the future would likely attempt to directly address the enzyme deficiency, so that normal metabolism of lipids might occur.

ORGANIZATIONS

Fatty Oxidation Disorders (FOD) Family Support Group. Deb Lee Gould, MEd, Director, FOD Family Support Group, MCAD Parent and Grief Consultant, 805 Montrose Dr., Greensboro, NC 24710. (336) 547-8682. <http://www.fodsupport.org>.

Genetic Alliance. 4301 Connecticut Ave. NW, #404, Washington, DC 20008-2304. (800) 336-GENE (Helpline) or (202) 966-5557. Fax: (888) 394-3937 info@geneticalliance. <http://www.geneticalliance.org>.

March of Dimes Birth Defects Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. (888) 663-4637. resourcecenter@modimes.org. <http://www.modimes.org>.

National Organization for Rare Disorders (NORD). PO Box 8923, New Fairfield, CT 06812-8923. (203) 746-6518 or (800) 999-6673. Fax: (203) 746-6481. <http://www.rarediseases.org>.

National Society of Genetic Counselors. 233 Canterbury Dr., Wallingford, PA 19086-6617. (610) 872-1192. <http://www.nsgc.org/GeneticCounselingYou.asp>.

United Mitochondrial Disease Foundation. PO Box 1151, Monroeville, PA 15146-1151. (412) 793-8077. Fax: (412) 793-6477. <http://www.umdf.org>.

OTHER

The Spiral Notebook—short takes on carnitine palmitoyl transferase deficiency. <http://www.spiralnotebook.org>

Scott J. Polzin, MS, CGC