Introduction:
Barth syndrome is a genetic condition characterized by an enlarged and weakened heart. It is a rare condition that primarily affects men. It usually presents as a congenital disability or develops within the first months of life. As it progresses, the heart becomes weaker and unable to pump blood. It is also called:
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X-linked endocardial fibroelastosis.
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3-methylglutaconic aciduria.
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X-linked cardioskeletal myopathy and neutropenia.
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Cardioskeletal myopathy with neutropenia and abnormal mitochondria.
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Endocardial fibroelastosis.
What Are the Clinical Features?
Barth Syndrome almost exclusively affects men. It is a very rare condition and is estimated to affect 1 in 300,000 to 400,000 individuals globally. Some of the symptoms include:
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Enlarged heart or dilated cardiomyopathy).
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Weakened heart.
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A low white blood cell count-neutropenia.
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Fatigue.
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Weakness of muscle used for movement- skeletal myopathy.
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Short stature.
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Distinct facial features such as prominent cheeks.
How Does the Disease Progress?
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Patients affected have elastic fibers in place of muscle fibers in some areas of the heart. This leads to cardiomyopathy and is called endocardial fibroelastosis. This leads to the thickening of the muscles and impairs the heart from pumping blood. In the majority of cases, these problems lead to heart failure. In some cases, it resolves over time, and the individuals have no symptoms of a heart condition.
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Muscles present close to the body become weak and low in tone (hypotonia). This is noticeable from birth, and this leads to the delay of motor skills such as walking and crawling. These individuals also experience extreme fatigue if subjected to strenuous exercise or physical activity.
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These individuals have normal intelligence but may find difficulty in solving tasks involving math and visual-spatial skills, such as puzzles.
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They have prominent cheeks and distinctive facial features.
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Blood and urine samples of affected males have increased levels of 3-methylglutaconic acid. This helps in diagnosing the disease but does not influence the condition.
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The affected males have reduced life expectancy. The affected children can die of heart failure or infections in infancy or early childhood. Those children who live into adulthood can survive up to their late forties. Cardiac muscle weakness leads to heart failure, and the reduced number of white blood cells makes the individual susceptible to infections.
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Even though the clinical features are distinctive and can be recognized at birth or infancy, the individuals may not experience health problems until later in life. And because of this, individuals with Barth syndrome may not be diagnosed early, and the severity of signs and symptoms may vary greatly.
How Is It Inherited?
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The cause of Barth syndrome is the mutation in a specific gene called Tafazzin. The gene associated with the condition is located on the X-chromosomes (one of the sex chromosomes); therefore, the condition mostly affects men. That is, the syndrome is inherited in an X-linked recessive pattern.
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If the affected copy of the gene is passed on to the male child, they are affected (since men have only one copy of the X-chromosome). Whereas in females, both copies of the chromosome should be affected for the disease to be expressed. If only one chromosome is affected, then they become carriers. Because the probability of women having two affected genes is low, the disease is rarely found in women.
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Another interesting characteristic is that the fathers will not pass the trait to their sons but will pass the abnormal gene to all their daughters, who will be carriers. Whereas if the mother is a carrier, there is a 25 % chance that the male child will inherit the X-chromosome that contains the abnormal gene; if so, he will develop the disease. Carrier females have a 25 % chance of having a carrier daughter, a noncarrier daughter, an unaffected son, and an affected son with each pregnancy.
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Tafazzin is responsible for altering a fat called cardiolipin which is found in mitochondria, which in turn is responsible for energy production needed for an organ. Therefore it is believed that loss of this gene affects the energy production in organs such as the heart and skeletal muscles leading to the condition.
How to Diagnose Barth Syndrome?
Barth syndrome is usually diagnosed during infancy or early childhood. But in some cases, the severity of symptoms varies; hence may be diagnosed later in life.
It is diagnosed based on clinical evaluation, detailed family history (since it can be inherited), physical findings, and specialized tests.
Barth syndrome can be suspected if someone has the following:
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Heart conditions such as hypertrophic cardiomyopathy and dilated cardiomyopathy.
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Increased levels of 3-methylglutaconic acid in urine or blood.
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Neutropenia- low white blood cell count.
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Hypotonia.
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Delay in milestones in infants, such as crawling and walking.
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Delay in growth.
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Multiple losses of pregnancies have been reported in some families with Barth syndrome involving male fetuses.
For confirmation of the disease, molecular genetic testing can be done.
How Is Barth Syndrome Treated?
Since it is a genetic condition, the treatment is based on the symptoms. And as the symptoms vary, it requires an interdisciplinary approach, including pediatricians, cardiologists that specialize in childhood heart disease, hematologists (to study the blood cells and tissues), and specialists to treat infections.
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Heart conditions may be treated with standard cardiac medications such as beta blockers, Digoxin, and ACE inhibitors. This helps to improve heart function and also reduces the risk of heart failure. A low dose of Aspirin is given to prevent clot formation. In severe cases, a heart transplant may be necessary. In some cases, the heart function improves after infancy, so transplant must be only considered in severe cases.
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For patients who have low white blood cell count and an increased tendency for bacterial infection, regular monitoring is required. If an infection is suspected, antibiotic therapy should be started early. In some cases, prophylactic (as preventive) antibiotics may be given.
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Physical therapy from early stages can help improve muscle tone and thereby help the child in attaining developmental milestones. Uncooked cornstarch before bedtime may help prevent muscle loss.
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If Barth syndrome is in the family, genetic counseling is recommended. If an individual is affected, the treatment is supportive and based on the symptoms.
Conclusion:
Barth syndrome is a rare genetic condition that mainly affects men. Affected individuals have poor muscle tone and decreased cardiac activity. The symptoms may start in infancy and may obstruct developmental milestones. The individuals may be easily fatigued, and heart conditions may progress to heart failure. The reduction in white blood cells makes them prone to infections. Genetic counseling may be required for families with a history of Barth syndrome. Diagnosis and treatment are based on symptoms.
