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Cardiomyopathy associated with carnitine loss in kidneys and small intestine
R Rodrigues Pereira1, H R Scholte, I E Luyt-Houwen
1Department of Paediatrics, St. Clara Hospital, Rotterdam, The Netherlands.
Insights
A boy with congestive cardiomyopathy had extremely low carnitine levels, suggesting a defect in carnitine transport. L-carnitine therapy successfully treated the cardiac condition.
Area of Science:
- Biochemistry
- Pediatrics
- Genetics
Background:
- Carnitine is essential for energy metabolism, particularly in the heart.
- Congestive cardiomyopathy can have various underlying causes, including metabolic disorders.
Observation:
- A 1-year-old boy presented with congestive cardiomyopathy and extremely low total plasma carnitine.
- Muscle carnitine was also significantly reduced, but without overt myopathy.
- Despite low carnitine, the patient lacked hypoglycemia, lactic acidemia, or dicarboxylic aciduria.
Findings:
- Carnitine loading increased liver carnitine but resulted in rapid urinary and fecal excretion, indicating impaired reabsorption.
- Isolated muscle mitochondria showed reduced oxidative capacity.
- Abnormally high renal clearance of carnitine suggested a defect in renal and intestinal transport systems.
Implications:
- This case highlights a potential defect in the brush border carnitine transport system.
- Early diagnosis and L-carnitine supplementation can effectively manage carnitine deficiency-related cardiomyopathy.
- Further research into carnitine transport mechanisms is warranted.
Abstract:
A boy was first seen at the age of 1 year on account of congestive cardiomyopathy. Growth and development had been normal. Total plasma carnitine was extremely low (1.8 mumol/l; normal range: 25-64 mumol/l). No hypoglycaemia, lactic acidaemia or dicarboxylic aciduria were found. Other laboratory findings were unremarkable except for a slight deficiency in iron, vitamin D and vitamin E. Total muscle carnitine was 1.5% of normal; however, no signs or symptoms of myopathy could be detected. After carnitine loading, liver carnitine increased to 24% of normal. Isolated muscle mitochondria showed decreased oxidative capacity with all substrates tested. Stimulation of O2 uptake by adenosine diphosphate (ADP) was decreased. After loading with both intravenous and oral carnitine, there was a rise in plasma carnitine and a rapid loss in the urine and the faeces. These findings suggest a defect in the brush border carnitine transport system of the kidneys and of the small intestine. Renal clearance of carnitine was abnormally high. Therapy with 1 g oral L-carnitine/kg per day was instituted without any problems and the cardiac disease resolved within 3 months. The parents and the patient's five sibs also had low plasma carnitine but displayed no cardiomyopathy.