Barth syndrome (BTHS)

Barth syndrome can affect people in different ways. It can include a range of signs and symptoms. Not everyone with Barth syndrome will have all of them.

Signs and symptoms may include:

• Heart muscle problems: The heart muscle may be weak, enlarged or have an unusual structure. This is called cardiomyopathy. It can make it harder for the heart to pump blood. Some people may also have heart rhythm problems.
• Muscle weakness and low muscle tone: Muscles may feel weak or floppy, especially muscles close to the centre of the body, such as the hips, shoulders and trunk. This may affect movement, posture and stamina.
• Neutropenia: Neutropenia means low levels of neutrophils. Neutrophils are white blood cells that help the body fight infections. Low neutrophil levels can increase the risk of infections, mouth ulcers and gum problems.
• Growth differences: Babies and children may grow more slowly than expected. Some may have delayed puberty, and some may have catch-up growth later.
• Low energy and fatigue: Some people may tire easily or have reduced stamina. Fatigue can affect school, work, play, exercise and daily activities. Fatigue has been reported across age groups.
• Feeding difficulties: Babies and children may have trouble with feeding, reflux, swallowing, picky eating or gaining weight.
• Delayed motor milestones: Some children may sit, crawl or walk later than expected because of muscle weakness, low muscle tone or reduced stamina.
• Exercise intolerance: Physical activity may feel harder than expected because the heart and muscles need a lot of energy.
• Higher levels of 3-methylglutaconic acid: This substance can sometimes be measured in urine. This may support diagnosis, but it may not be present in every person with Barth syndrome.

Other signs and symptoms may include:

• shortness of breath or tiredness linked to heart problems
• frequent bacterial infections
• low blood sugar, especially during illness or poor feeding
• lactic acidosis
• lower-than-normal cholesterol levels
• constipation or diarrhoea
• low bone density
• scoliosis, which is a curve in the spine
• distinctive facial features in infancy or childhood
• learning or attention differences in some people.

This section combines information from trusted sources.^2–4,6,8 The explanations have been adapted into plain language by Mito Foundation.

For more information

Understand the signs and symptoms of mito

Barth syndrome is caused by changes in nuclear DNA. Nuclear DNA is the DNA stored in the centre of the cell, within the nucleus.

Genes are the basic physical and functional units of heredity. They are made up of DNA. They give the body instructions for making proteins. Barth syndrome is linked to changes in the TAFAZZIN gene, formally called TAZ. ⁹ This gene helps the body make a protein called tafazzin. Tafazzin helps maintain cardiolipin. Cardiolipin is a fat-like substance found in mitochondria.^2,10 

Mitochondria are parts of cells that help make energy. Cardiolipin helps mitochondria keep their structure and make energy.

When the TAFAZZIN gene is changed, tafazzin may not work as expected. This can affect cardiolipin and energy production.¹¹ This often affects parts of the body that need a lot of energy, such as the heart, muscles and immune system.^2,12 

Barth syndrome is a genetic condition. It is not caused by diet, lifestyle or anything a parent did or did not do.

How is Barth syndrome inherited?

Barth syndrome is usually inherited in an X-linked pattern. This means the gene change is on the X chromosome.⁹ 

X-linked inheritance describes how a gene change can be passed through families. It can affect males and females differently because they usually have different sex chromosomes.

Why Barth syndrome usually affects males

Males have one X chromosome from their mother and one Y chromosome from their father. If a male inherits an X chromosome with the Barth syndrome gene change, he is likely to have Barth syndrome. This is because he does not have a second X chromosome with a working copy of the gene.

The effects can vary from person to person. Some people may have milder symptoms or develop symptoms later.^2,6 

If a male with Barth syndrome has children, all his daughters will be carriers of the gene change. His sons will not inherit the gene change from him. This is because fathers usually pass their Y chromosome to their sons and their X chromosome to their daughters.

Can females have Barth syndrome?

It is extremely rare for females to have Barth syndrome. However several females have been confirmed as having the condition.

Females usually have 2 X chromosomes. Females who have the gene change on one of their X chromosomes are called carriers. Carriers usually do not show symptoms because their other X chromosome can help make up for the X chromosome with the gene change.

If a female carrier of Barth syndrome has children, each child has a 1 in 2 chance of inheriting the gene change. A boy born to a female carrier will have a 50% chance of having Barth syndrome, whereas girls born to a female carrier will have a 50% risk of being carriers themselves. All daughters of a male with Barth syndrome will be carriers, however his sons will not be affected.

Additional information

Barth syndrome can occur without a known family history. In some people, the change in the TAFAZZIN gene is new and was not inherited from either parent. This is called a de novo gene change. The term ‘de novo’ means ‘new’.

De novo TAFAZZIN gene changes have been reported in people with Barth syndrome. Published reports suggest they are less common than gene changes inherited from a person’s mother.^13,14 

A de novo gene change can still be passed on to children.¹⁵ The inheritance pattern depends on the sex chromosomes a person passes on, as explained above.

Symptoms and severity can vary, including within families.^2,6 Genetic testing can help identify a change in the TAFAZZIN gene. Results may need to be considered with symptoms, family history and clinical assessment.

For more information

Learn more about genetics and mito

Information to understand your diagnosis

Information to understand your child’s diagnosis

Signs of Barth syndrome often appear in babies or young children. Some people are diagnosed later in childhood or, rarely, in adulthood.^16,17

Diagnosis usually involves looking at the person’s symptoms, medical history, family history, physical examination and test results.

A health professional may suspect Barth syndrome when a baby, child or adult has a combination of:

• heart muscle problems, including cardiomyopathy
• neutropenia or frequent infections
• muscle weakness or low muscle tone
• slower growth or feeding difficulties
• delayed motor milestones
• a family history that suggests an X-linked condition.

The body systems checked may include the heart, muscles, immune system, growth, feeding and development.

Tests may include:

• Physical examination: A doctor may check growth markers such as height and weight, and look for signs of muscle weakness or low muscle tone.
• Genetic testing: This looks for changes in the TAFAZZIN. It can help support or confirm a diagnosis. A blood or saliva sample may be used, and results may take several months.
• Cardiolipin testing: This looks at the balance between monolysocardiolipin and cardiolipin. People with Barth syndrome often have too much monolysocardiolipin and not enough mature cardiolipin. This pattern can support a diagnosis. This is sometimes called the MLCL to CL ratio.
• Blood tests: These may check neutrophil levels, signs of infection, blood sugar, lactate and other markers. Neutrophil levels can change over time, so more than one test may be needed.
• Urine tests: These may check for 3-methylglutaconic acid and other organic acids. This can support diagnosis. A normal result does not always rule out Barth syndrome.
• Heart tests: An electrocardiogram, also called an ECG, checks heart rhythm. An echocardiogram uses ultrasound to look at the heart’s structure and pumping function. Some people may also have longer heart rhythm monitoring.
• Growth, feeding and development checks: These may look at growth, weight gain, feeding, swallowing, movement, muscle strength, learning and daily activities.

Genetic counselling may be offered. Genetic counselling is not the same as emotional counselling. It can help explain what test results may mean for the person and their family. It may also help with testing and what results could mean for relatives. Testing may also help rule out other conditions that can cause similar heart, muscle, immune or growth symptoms.

For more information

Learn more about genetics and mito

Elamipretide is a medicine approved by the United States, which has Food and Drug Administration (FDA) accelerated approval for Barth syndrome in certain people.¹ 

Active ingredient: elamipretide 

Brand name: Forzinity 

Other names used in research: elamipretide hydrochloride, SS-31 and MTP-131 

The active ingredient is the name of the medicine itself. The brand name is the name used by the company that makes it. Some research may use other names. 

Elamipretide is a medicine being studied for its effects on mitochondria, the parts of cells that produce energy. It works by attaching to cardiolipin, a type of fat found in the inner membrane of mitochondria. In Barth syndrome, changes in the TAFAZZIN gene affect how cardiolipin is formed and maintained, which can disrupt how mitochondria work.^2,3  

In the United States, elamipretide has accelerated approval for people with Barth syndrome. This decision was based on results from clinical trials. Accelerated approval allows medicines to be made available based on early evidence of benefit, with further studies required to confirm how well they work.¹

Elamipretide is not a cure for Barth syndrome. 

What this means in Australia 

Current as at July 2026, elamipretide is not approved by the Therapeutic Goods Administration (TGA) in Australia. The TGA is the Australian Government agency that checks medicines for safety, quality and effectiveness before they can be supplied in Australia through the usual approval pathway. 

This information can change over time. Mito Foundation’s elamipretide for Barth syndrome page has more information about: 

• whether elamipretide is approved in Australia 
• who it may be relevant for 
• what research has been done 
• what is still unknown 
• possible risks and side effects 
• clinical trial information. 

Read Mito Foundation’s elamipretide for Barth syndrome page. 

Mito Foundation provides information to help people affected by mito understand clinical trials and how to find opportunities that may be relevant to them.

Clinical trials help researchers test new ways to prevent, diagnose, treat and manage mito. Some trials test whether a treatment is safe and whether it may help people.

Other clinical studies may look at symptoms, diagnosis, genetics, quality of life, or how mito affects people over time.

Clinical trials are carefully planned. The therapies being studied may be at different stages. Trials may not be available for every type of mito, and not every trial will be right for you. Some trials are only open to people with a confirmed genetic diagnosis, specific symptoms, a certain age range, or the ability to attend study appointments.

Mito Foundation’s emerging therapies information explains therapies in development, how clinical trials work, and what you may wish to consider before taking part. You can also use the Therapy Finder to explore therapies in development and see what may be relevant to you.

Learn more about taking part in clinical trials
Use the Therapy Finder

Staying informed

One way to hear about opportunities to take part in clinical trials is to join the Mito Registry.

The Mito Registry helps connect people with research opportunities that may be relevant to them. It also helps Mito Foundation understand how many people in Australia are affected by different types of mito.

This information can help support future research, services and advocacy.

Join the Mito Registry

The Barth Syndrome Foundation (US) provides fact sheets about Barth syndrome for individuals, families and health professionals.

This is a US-based resource. Information about clinical care, medicines, services and treatment access may differ from the Australian context. A health professional familiar with Barth syndrome can help explain how the information may apply in Australia.

Read Barth Syndrome Foundation fact sheets (US)

Additional information

National Organisation for Rare Disorders (NORD), Barth Syndrome (US)

Genetic and Rare Diseases (GARD) Information Centre – Barth Syndrome (US)

Australia-based Facebook groups 

Mito Support Community 

As of July 2026, no active support groups dedicated to Barth syndrome were found in Australia.

Global Facebook groups for ADOA 

Barth Syndrome Foundation Facebook Group (US)