What Is Barth Syndrome? Symptoms, Causes, and Treatment
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What is Barth syndrome?
Barth syndrome is a rare X-linked genetic disorder, mainly affecting boys, in which a TAZ gene change stops mitochondria from producing enough energy, damaging the heart, muscles and white blood cells. [3] It causes cardiomyopathy, low neutrophil counts, muscle weakness and growth delays. [2] There is no cure, but heart medicines, antibiotics and G-CSF manage symptoms, and survival has improved dramatically.
Key takeaways
Barth syndrome is a rare genetic disorder that mainly affects boys and typically begins in infancy or early childhood. [4]
It is caused by a change in the TAZ gene, which damages the energy-producing mitochondria in cells. [3]
The condition affects the heart, white blood cell levels, muscles, and growth, and can also cause feeding problems, learning difficulties, and distinctive facial features. [2] [4]
There is no cure, but symptoms are managed with heart medications, antibiotics, G-CSF, therapies, and nutritional support.
Survival has improved significantly: babies born in or after 2000 have a five-year survival rate of 70%, and many people live into adulthood. [1] [2]
Researchers are testing promising new treatments, including SS-31, MA-5, and gene therapy targeting the TAZ gene.
What the research says
Barth syndrome is X-linked, and the heart is often where it first shows. A 2025 narrative review explains that males who inherit the pathogenic variant develop the condition while females generally do not. It also notes that heart involvement ranges from a severely dilated heart to a hypertrophic one, with left ventricular non-compaction occasionally seen, and that the cardiac picture may reveal the prognosis (Sergi, Genes, 2025). [5]
A drug that targets mitochondria has gained accelerated approval for muscle strength. A 2026 review reports that elamipretide has accelerated approval for improving muscle strength in patients with Barth syndrome weighing at least 30 kg, while any benefit for heart disease remains unconfirmed (Lee et al., Int J Mol Sci, 2026). [6]
MA-5 improved Barth syndrome features in laboratory models. In patient-derived cells and a fruit fly model, mitochonic acid 5 improved mitochondrial function, reduced cell death from oxidative stress, and improved movement and the fast heartbeat seen in the model. These are laboratory findings, not results in patients (Tongu et al., FASEB J, 2025). [7]
What Is Barth Syndrome?
Barth syndrome is a rare genetic disorder that mainly affects boys. It causes serious health issues that usually begin in infancy or early childhood. [4]
The condition affects four major areas of health: [2]
Heart conditions
Immune system issues
Muscle weakness
Growth delays
The problem starts inside the body's cells. It is caused by a change in a gene called TAZ (also called TAFAZZIN). [2] This gene supports tiny structures in cells called mitochondria, which turn the food a child eats into energy the body can use.
When the TAZ gene does not work the way it should, a type of fat called cardiolipin does not form correctly. This makes it harder for mitochondria to do their job, leading to the signs and symptoms of the condition. [3]
In the past, many children with Barth syndrome did not live past early childhood because of heart failure or infections. Today, earlier diagnosis and improved treatments mean many people with the condition live into adulthood. It is still a serious, lifelong condition, and symptoms can change or become life-threatening very quickly.
What Are the Symptoms of Barth Syndrome?
Symptoms can vary from child to child, but they commonly include heart problems, low white blood cell levels, low muscle mass, and growth delay. [1] [2]
Heart problems
A baby with Barth syndrome may be born with dilated cardiomyopathy. [3] As the child gets older, these problems can lead to heart failure.
Heart condition | What it means |
Dilated cardiomyopathy | The heart muscle becomes enlarged and weakened [4] |
Hypertrophic cardiomyopathy | The heart muscle becomes thickened [4] |
Endocardial fibroelastosis | Elastic fibers form in the heart muscle |
Left ventricular non-compaction | The lower left heart chamber becomes spongy and thickened [4] |
Arrhythmia | An irregular heartbeat that develops as the child gets older [4] |
Neutropenia (low white blood cells)
Neutropenia means the child has low levels of a type of white blood cell called neutrophils. Neutrophils help the body fight infections. Low levels make it harder to fight off bacteria and viruses, raising infection risk and potentially leading to sepsis.
Type of neutropenia | What it means |
Cyclic | Neutrophil levels cycle in regular intervals between normal and low |
Intermittent | No predictable pattern; levels vary from normal to low |
Chronic | Always present; levels stay consistently low |
Low muscle mass
Barth syndrome can cause muscle weakness (skeletal myopathy) and low muscle tone (hypotonia). Both can lead to extreme fatigue and delays in motor skills, such as learning to crawl and walk. [2] [4]
Low muscle mass also affects a child's ability to go long between meals. Because the body does not store enough energy, children are always at risk of low blood sugar (hypoglycemia).
Growth delay
Most babies with Barth syndrome are smaller than average at birth, and they may remain shorter and lighter than average throughout childhood. Growth usually speeds up during puberty, and most children eventually reach an average to above-average height and weight.
Other signs and symptoms
Symptom | What it looks like |
Feeding problems | Trouble sucking or swallowing, picky eating, frequent vomiting [1] |
High organic acid levels | Unusually high organic acids in blood and urine (3-methylglutaconic aciduria) [4] |
Bone abnormalities | Curvature of the spine (scoliosis) [4] |
Learning disabilities | Especially in math and visual-spatial skills, like reading a map or solving a puzzle |
Facial features
Children with Barth syndrome may have distinctive facial features, including a round face, pointed chin, full cheeks, large ears, and deep-set eyes. These features may become less noticeable as the child gets older. [2]
What Causes Barth Syndrome?
Genetic changes (variants) in the TAZ gene cause Barth syndrome (see our guide to genetic mutations). This gene makes a protein called tafazzin. [4] Tafazzin helps the energy-producing part of cells (mitochondria) work properly and alters a fat called cardiolipin, which supports the mitochondria's shape, energy production, and protein movement.
Here is how the problem develops, step by step:
Step | What happens |
1 | The TAZ gene does not work correctly |
2 | The protein tafazzin is missing or weak |
3 | Cardiolipin cannot form its healthy shape, and a different fat called monolysocardiolipin (MLCL) builds up instead |
4 | Mitochondria cannot make enough energy and stop functioning properly |
5 | Tissues with the highest energy demand die: the heart, muscles, and certain white blood cells |
6 | The signs and symptoms of Barth syndrome appear |
How is Barth syndrome inherited?
Barth syndrome is passed down in an X-linked recessive pattern. This means it mostly affects boys, because they have only one X chromosome. [3]
How Is Barth Syndrome Diagnosed?
Diagnosis usually happens during infancy or early childhood. A provider performs a physical exam looking for common signs, including heart problems, immune system issues, weak muscles, and unique facial features. Because the condition is inherited in an X-linked pattern, the provider will also ask about biological family history.
Tests used for diagnosis
Two main lab tests can confirm a Barth syndrome diagnosis:
A provider may also order these supporting tests:
Supporting test | What it does |
Urine test | Checks for abnormal organic acid levels [2] |
Complete blood count | Measures white blood cell levels [2] |
Echocardiogram | An ultrasound of the heart that checks its structure and function |
Heart monitor | A sticker placed on the chest that records heart rhythm for short periods |
Growth tracking | Monitors height and weight over time |
How Is Barth Syndrome Treated?
There is no cure for Barth syndrome. Treatment focuses on managing symptoms, monitoring heart function, and preventing complications.
Treatment | How it helps |
Routine cardiac observation | Echocardiograms and heart monitors check for fast heart rhythms |
Heart medications | Beta-blockers and ACE inhibitors help the heart work better if it is not functioning properly [4] |
Aspirin | |
Antibiotics | |
G-CSF | Helps the body make more white blood cells |
Cornstarch at bedtime | |
Physical and occupational therapy | Build strength, improve movement, and support development |
Feeding tube | Helps a child gain weight when regular feeding is not enough |
Promising new treatments under research
Researchers are testing new treatment options. Most are not yet approved, but they show promise as future therapies:
Experimental treatment | What it does |
SS-31 | A drug (also called elamipretide) that attaches to cardiolipin and helps mitochondria keep their shape and work more efficiently; it has received accelerated approval for improving muscle strength in people with Barth syndrome who weigh at least 30 kg, but benefit for the heart has not been confirmed |
MA-5 | A drug that reduces stress in cells and helps mitochondria make more energy; in lab studies, it improved heart health and muscle strength |
Gene therapy | Scientists are testing ways to repair or replace the TAZ gene; a version called TAFAZZIN-Antp may enter cells better and help prevent heart damage |
What Is the Life Expectancy With Barth Syndrome?
Some people with Barth syndrome live into their 30s, while others live into their 60s. The highest chance of early death is in the first few years of life. [2]
Survival depends on three main factors:
Survival factor | What the data shows |
Neutrophil levels | Infants with fewer than 500 neutrophils per microliter at diagnosis have a one-year survival rate of 25%; infants with more than 500 have a one-year survival rate of 68% [2] |
Birth year | Infants born before 2000 had a five-year survival rate of 22%; infants born in or after 2000 have a five-year survival rate of 70%, likely because of improved heart treatments |
Heart-related complications | Some children who develop heart failure at an early age may need a heart transplant, depending on disease severity [2] |
What Is the Outlook?
Life with Barth syndrome can be challenging. It is normal to worry about a child's heart, muscles, and energy level. Their body works hard every day, even when symptoms make things difficult.
Available treatments support the child day to day, but emerging research also offers real reasons for hope. Scientists are studying ways to help cells make more energy and improve heart and muscle health. One day, these promising treatments may help children with Barth syndrome grow stronger and live a fuller life.
Conclusion
Barth syndrome is a rare, serious genetic disorder that mainly affects boys. A change in the TAZ gene disrupts the mitochondria, the tiny energy factories inside cells, which damages the heart, muscles, and immune system. While there is no cure, modern care, including heart monitoring, medications, infection prevention, and therapies, has transformed the outlook dramatically, with most children born in or after 2000 surviving past age five and many living into adulthood.
If you notice heart problems, frequent infections, muscle weakness, or unusual growth patterns in your child, talk to a pediatrician about whether genetic testing is appropriate. Understanding the condition early gives your child the best chance at strong, supported health.
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Frequently Asked Questions
What is Barth syndrome?
Barth syndrome is a rare genetic disorder that mainly affects boys. It causes heart problems, low white blood cell counts, muscle weakness, and growth delays, usually starting in infancy or early childhood. It is caused by a change in the TAZ gene that disrupts the body's mitochondria. [3] [4]
Who gets Barth syndrome?
Barth syndrome mostly affects boys, because it is inherited in an X-linked recessive pattern and boys have only one X chromosome. [3] A mother who carries the gene variant has a 50% chance of passing it on. Females who inherit it may become carriers. [2]
What causes Barth syndrome?
Genetic changes in the TAZ gene cause the condition. The gene makes a protein called tafazzin, which helps mitochondria work properly. [3] [4] When the gene is faulty, a fat called cardiolipin cannot form correctly, and a different fat (MLCL) builds up instead. This starves high-energy tissues: the heart, muscles, and certain white blood cells.
What are the main symptoms?
The most common symptoms are heart conditions, low white blood cell counts (neutropenia), low muscle mass, and growth delays. [1] [2] Feeding problems, high organic acid levels, bone abnormalities such as scoliosis, and learning disabilities, especially in math and visual-spatial skills, may also occur. [4]
What heart problems does Barth syndrome cause?
Babies may be born with dilated cardiomyopathy, hypertrophic cardiomyopathy, endocardial fibroelastosis, or left ventricular non-compaction. As children grow, they may develop an irregular heartbeat (arrhythmia), which can eventually lead to heart failure.
Why do children with Barth syndrome get sick so easily?
The condition causes neutropenia: low levels of neutrophils, the white blood cells that fight bacteria and viruses. This makes it harder for the body to fight infections and can lead to sepsis. [2] Neutropenia can be cyclic, intermittent, or chronic. [1]
Is there a cure for Barth syndrome?
No. There is currently no cure. Treatment focuses on managing symptoms, monitoring heart function, and preventing complications through medications, therapies, nutritional support, and regular cardiac observation.
How is Barth syndrome diagnosed?
Diagnosis typically happens in infancy or early childhood through a physical exam and family history review. Two main lab tests confirm it: genetic testing for TAZ gene variants and the MLCL/CL ratio test, which finds too much MLCL and not enough cardiolipin in blood and tissues. [2]
What treatments are available?
Treatments include routine cardiac observation, heart medications (beta-blockers, ACE inhibitors), aspirin, antibiotics, G-CSF to boost white blood cells, bedtime cornstarch to prevent muscle loss, physical and occupational therapy, and sometimes a feeding tube.
What experimental treatments are being researched?
Researchers are testing SS-31 (also called elamipretide, a drug that helps mitochondria keep their shape, which has received accelerated approval for improving muscle strength in people weighing at least 30 kg), MA-5 (a drug that reduces cell stress and boosts energy production), and gene therapy to repair or replace the TAZ gene, including a version called TAFAZZIN-Antp that may enter cells better.
What is the life expectancy with Barth syndrome?
Some people live into their 30s and others into their 60s. The highest risk of early death is in the first few years of life. Survival has improved greatly: infants born in or after 2000 have a five-year survival rate of 70%, compared to 22% for those born before 2000. [2]
What determines survival?
Three factors matter most: neutrophil levels at diagnosis (fewer than 500 cells per microliter means a 25% one-year survival rate; more than 500 means 68%), birth year (post-2000 births fare much better due to improved heart treatments), and heart complications (severe early heart failure may require a transplant).
What facial features are associated with Barth syndrome?
Children may have a round face, pointed chin, full cheeks, large ears, and deep-set eyes. These distinctive features often become less noticeable as the child gets older. [2]
Can children with Barth syndrome catch up in growth?
Most babies are smaller than average at birth and may stay smaller through childhood. However, children typically grow quickly during puberty and often reach an average to above-average height and weight.
When should I see a pediatrician?
Seek evaluation if your child has heart problems, frequent infections, muscle weakness, extreme fatigue, feeding difficulties, or slower-than-expected growth. Early diagnosis is one of the strongest factors in improving outcomes for children with Barth syndrome.
Related Reading
References
Barth Syndrome Foundation. What is Barth Syndrome? Barth Syndrome Foundation. Last updated March 3, 2019. Accessed May 12, 2026. https://www.barthsyndrome.org/barthsyndrome/
GeneReviews: Barth Syndrome. National Center for Biotechnology Information (NCBI Bookshelf). Updated January 8, 2026. Accessed May 12, 2026. https://www.ncbi.nlm.nih.gov/books/NBK247162/
MedlinePlus Genetics. Barth syndrome. U.S. National Library of Medicine. Last updated November 24, 2021. Accessed May 12, 2026. https://medlineplus.gov/genetics/condition/barth-syndrome/
National Organization for Rare Disorders. Barth Syndrome. NORD Rare Disease Database. Last updated September 22, 2025. Accessed May 12, 2026. https://rarediseases.org/rare-diseases/barth-syndrome
Sergi CM. Barth syndrome: gene, cardiologic aspects, and mitochondrial studies. A comprehensive narrative review. Genes (Basel). 2025;16(4):465. PMID: 40282425. https://doi.org/10.3390/genes16040465
Lee CL, Chuang CK, Chang YH, et al. Mitochondrial quality control in inherited mitochondrial cardiomyopathy: convergent pathobiology and a testable therapeutic framework. Int J Mol Sci. 2026;27(18):8270. PMID: 42794697. https://doi.org/10.3390/ijms27188270
Tongu Y, Kasahara T, Matsuhashi T, et al. Mitochondria-homing drug mitochonic acid 5 improves Barth syndrome myopathy in a human-induced pluripotent stem cell model and Barth syndrome Drosophila model. FASEB J. 2025;39(12):e70739. PMID: 40542649. https://doi.org/10.1096/fj.202401856RRR
Medical disclaimer
The information provided in this article is for educational purposes only and is not intended as medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition, including diagnosis and treatment decisions specific to your child's health.
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