Barth syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Barth syndrome is a rare condition characterized by an enlarged and weakened heart (dilated cardiomyopathy), weakness in muscles used for movement (skeletal myopathy), recurrent infections due to small numbers of white blood cells (neutropenia), and short stature. Barth syndrome occurs almost exclusively in males.

In males with Barth syndrome, dilated cardiomyopathy is often present at birth or develops within the first months of life. Over time, the heart muscle becomes increasingly weakened and is less able to pump blood. Individuals with Barth syndrome may have elastic fibers in place of muscle fibers in some areas of the heart muscle, which contributes to the cardiomyopathy. This condition is called endocardial fibroelastosis; it results in thickening of the muscle and impairs its ability to pump blood. In people with Barth syndrome, the heart problems can lead to heart failure. In rare cases, the cardiomyopathy gets better over time and affected individuals eventually have no symptoms of heart disease.

In Barth syndrome, skeletal myopathy, particularly of the muscles closest to the center of the body (proximal muscles), is usually noticeable from birth and causes low muscle tone (hypotonia). The muscle weakness often causes delay of motor skills such as crawling and walking. Additionally, affected individuals tend to experience extreme tiredness (fatigue) during strenuous physical activity.

Most males with Barth syndrome have neutropenia. The levels of white blood cells can be consistently low (persistent), can vary from normal to low (intermittent), or can cycle between regular episodes of normal and low (cyclical). Neutropenia makes it more difficult for the body to fight off foreign invaders such as bacteria and viruses, so affected individuals have an increased risk of recurrent infections.

Newborns with Barth syndrome are often smaller than normal, and their growth continues to be slow throughout life. Some boys with this condition experience a growth spurt in puberty and are of average height as adults, but many men with Barth syndrome continue to have short stature in adulthood.

Males with Barth syndrome often have distinctive facial features including prominent cheeks. Affected individuals typically have normal intelligence but often have difficulty performing tasks involving math or visual-spatial skills such as puzzles.

Males with Barth syndrome have increased levels of a substance called 3-methylglutaconic acid in their blood and urine. The amount of the acid does not appear to influence the signs and symptoms of the condition. Barth syndrome is one of a group of metabolic disorders that can be diagnosed by the presence of increased levels of 3-methylglutaconic acid in urine (3-methylglutaconic aciduria).

Even though most features of Barth syndrome are present at birth or in infancy, affected individuals may not experience health problems until later in life. The age at which individuals with Barth syndrome display symptoms or are diagnosed varies greatly. The severity of signs and symptoms among affected individuals is also highly variable.

Males with Barth syndrome have a reduced life expectancy. Many affected children die of heart failure or infection in infancy or early childhood, but those who live into adulthood can survive into their late forties.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in the TAFAZZIN gene cause Barth syndrome. The TAFAZZIN gene provides instructions for making a protein called tafazzin. This protein is located in structures called mitochondria, which are the energy-producing centers of cells. The tafazzin protein is involved in altering a fat (lipid) called cardiolipin, which plays critical roles in the mitochondrial inner membrane. Once altered by tafazzin, cardiolipin is key in maintaining mitochondrial shape, energy production, and protein transport within cells.

TAFAZZIN gene mutations result in the production of tafazzin proteins with little or no function. As a result, tafazzin cannot alter cardiolipin, and levels of functional cardiolipin are reduced. In addition, for unknown reasons, a variant of cardiolipin called monolysocardiolipin (MLCL) is formed. A lack of functional cardiolipin and an excess of MLCL are thought to impair normal mitochondrial shape and functions. Tissues with high energy demands, such as the heart and skeletal muscles, are most susceptible to cell death due to reduced energy production in mitochondria. Additionally, abnormally shaped mitochondria are found in affected white blood cells, which could affect their ability to grow (proliferate), mature (differentiate), and function, leading to neutropenia. Dysfunctional mitochondria likely lead to other signs and symptoms of Barth syndrome.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an X-linked recessive pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders much more frequently than females. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Barth syndrome is estimated to affect 1 in 300,000 to 400,000 individuals worldwide. More than 150 cases have been described in the scientific literature.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

3-Methylglutaconic aciduria · Very frequent (99-80%)

An increased amount of 3-methylglutaconic acid in the urine.

Dilated cardiomyopathy · Very frequent (99-80%)

Dilated cardiomyopathy (DCM) is defined by the presence of left ventricular dilatation and left ventricular systolic dysfunction in the absence of abnormal loading conditions (hypertension, valve disease) or coronary artery disease sufficient to cause global systolic impairment. Right ventricular dilation and dysfunction may be present but are not necessary for the diagnosis.

Skeletal myopathy · Very frequent (99-80%)

3-Methylglutaric aciduria · Frequent (79-30%)

An abnormally increased level of 3-hydroxy-3-methylglutaric acid in the urine.

Anxiety · Frequent (79-30%)

Intense feelings of nervousness, tension, or panic often arise in response to interpersonal stresses. There is worry about the negative effects of past unpleasant experiences and future negative possibilities. Individuals may feel fearful, apprehensive, or threatened by uncertainty, and they may also have fears of falling apart or losing control.

Arrhythmia · Frequent (79-30%)

Any cardiac rhythm other than the normal sinus rhythm. Such a rhythm may be either of sinus or ectopic origin and either regular or irregular. An arrhythmia may be due to a disturbance in impulse formation or conduction or both.

Broad forehead · Frequent (79-30%)

Width of the forehead or distance between the frontotemporales is more than two standard deviations above the mean (objective); or apparently increased distance between the two sides of the forehead.

Decreased circulating prealbumin concentration · Frequent (79-30%)

The concentration of prealbumin in the blood circulation is below the lower limit of normal.

Other findings in the same source

From: Orphanet

Additional reported features include Decreased total neutrophil count (Frequent (79-30%)); Deeply set eye (Frequent (79-30%)); Delayed gross motor development (Frequent (79-30%)); Delayed skeletal maturation (Frequent (79-30%)); Elevated circulating hepatic transaminase concentration (Frequent (79-30%)); Elevated monolysocardiolipin/cardiolipin ratio (Frequent (79-30%)); Endocardial fibroelastosis (Frequent (79-30%)); Exercise intolerance (Frequent (79-30%)); Full cheeks (Frequent (79-30%)); Hypocholesterolemia (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Barth syndrome is Metabolic Medicine, with a metabolic specialist / clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with metabolic specialist / clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Is a biochemical or molecular result needed to clarify the diagnosis?
• Does this condition require an individual plan for illness or reduced food intake?
• Should nutrition advice come from a specialist metabolic dietitian?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Barth syndrome. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.