From the Guidelines
Symptoms of carnitine deficiency include muscle weakness, fatigue, confusion, heart rhythm abnormalities, and low blood sugar, as well as muscle pain, reduced exercise tolerance, and cardiomyopathy, which can lead to severe morbidity and mortality if left untreated. According to the most recent and highest quality study 1, carnitine deficiency can be primary or secondary, with primary carnitine deficiency being a genetic disorder that usually manifests itself by five years of age with symptoms of cardiomyopathy, skeletal muscle weakness, and hypoglycemia. Secondary carnitine deficiencies may occur in chronic renal failure, or under particular conditions that reduce carnitine absorption or increase its excretion.
Some of the key symptoms of carnitine deficiency include:
- Muscle weakness and fatigue
- Confusion and heart rhythm abnormalities
- Low blood sugar and hypoglycemia
- Muscle pain and reduced exercise tolerance
- Cardiomyopathy and heart muscle disease
- Poor feeding, irritability, and developmental delays in infants and children
- Metabolic crises characterized by vomiting, lethargy, and encephalopathy, particularly during periods of fasting or illness
The biologic effects of low carnitine levels may not be clinically significant until they reach less than 10-20% of normal, but profound carnitine deficiency can cause hypoketotic hypoglycemia, muscle weakness, rhabdomyolysis, cardiomyopathy, arrhythmia, and sudden death 1. Treatment typically involves L-carnitine supplementation, with doses ranging from 50-100 mg/kg/day divided into 2-3 doses, and higher doses sometimes needed for primary carnitine deficiency 1. Dietary adjustments and regular monitoring of carnitine levels are also important components of management.
It is essential to note that while some studies suggest a beneficial effect of L-carnitine supplementation for maintenance dialysis patients, the evidence is not conclusive, and the use of L-carnitine should be considered on a case-by-case basis, particularly in patients with symptoms suggestive of carnitine deficiency and who have not responded to standard therapies 1.
From the FDA Drug Label
In the reported cases, the clinical presentation consisted of recurrent episodes of Reye-like encephalopathy, hypoketotic hypoglycemia, and/or cardiomyopathy. Associated symptoms included hypotonia, muscle weakness and failure to thrive The symptoms of carnitine (L-carnitine) deficiency include:
- Reye-like encephalopathy
- Hypoketotic hypoglycemia
- Cardiomyopathy
- Hypotonia
- Muscle weakness
- Failure to thrive 2
From the Research
Symptoms of Carnitine Deficiency
The symptoms of carnitine (L-carnitine) deficiency can be categorized into different areas, including:
- Metabolic encephalopathy
- Lipid storage myopathy
- Cardiomyopathy 3
- Impairment of long-chain fatty acid metabolism and failure of energy production affecting tissues reliant on oxidative metabolism 3
- Hypoketotic hypoglycemia, transaminase elevations, and hyperammonemia due to the accumulation of toxic fatty acyl derivatives 3
- Dicarboxylic aciduria resulting from the oxidation of accumulated fatty acids through an alternative pathway, omega-oxidation 3
Specific Symptoms
Some specific symptoms associated with carnitine deficiency include:
- Hypotonia (low muscle tone)
- Muscle weakness
- Motor skills impairment
- Muscle wasting 4
- Myopathic symptoms due to defective carnitine transport into skeletal muscle 3
- Cardiomyopathy, which can be progressive and severe 5, 6
- Proximal limb weakness 6
Secondary Carnitine Deficiency Symptoms
Secondary carnitine deficiency can occur due to various conditions, including:
- Inborn errors of metabolism
- Acquired medical conditions such as cirrhosis, chronic renal failure, diabetes mellitus, and heart failure 7
- Medication side effects, for example, valproate and zidovuline treatment 7
- Increased catabolism, as seen in critical illness 7
- Preterm neonates due to impaired proximal renal tubule carnitine re-absorption and immature carnitine biosynthesis 7