Monday, April 16, 2012

Barth Syndrome (BTHS)

Overview: Barth syndrome (BTHS) is a rare, sex-linked genetic disorder of lipid metabolism that primarily affects males across different ethnicities. Typically, boys with BTHS present with hypotonia (low muscle tone) and dilated cardiomyopathy (labored breathing, poor appetite, and/or slow weight gain) at or within the first few months after birth. Other important features of BTHS include bacterial infections because of neutropenia (a reduction in the number of white blood cells called neutrophils), muscle weakness, fatigue, and growth delay. Although most children with BTHS manifest all of these characteristics, some have only one or two of these abnormalities and, as a result, often are given incorrect diagnoses.

Barth syndrome occurs in many different ethnic groups and does not appear to be more common in any one group. To date, there are no good studies of the population or birth incidence of BTHS. The gene for Barth syndrome, tafazzin (TAZ, also called G4.5), is located on the long arm of the X chromosome (Xq28). Mutations in the tafazzin gene lead to decreased production of an enzyme required for the synthesis of “cardiolipin,” a special lipid that is important in energy metabolism.

A weak heart muscle usually associated with enlargement of the heart (usually dilated with variable myocardial hypertrophy, sometimes with left ventricular noncompaction and/or endocardial fibroelastosis).

(Chronic, Cyclic, or Intermittent) A reduction in “neutrophils,” a type of white blood cell that is most important for fighting bacterial infections. Neutropenia may predispose an individual to mouth ulcers, fevers and bacterial infections such as bacterial pneumonia and skin abscesses.
Underdeveloped Skeletal Musculature and Muscle Weakness All muscles, including the heart, have a cellular deficiency which limits their ability to produce energy. Muscle weakness and increased exertional fatigue are characteristic findings in BTHS.

Growth Delay
During childhood most affected individuals are below-average in height and weight. This is often assumed to be evidence of poor nutrition or other secondary effects of a chronic illness, but that is rarely the case. In fact, some of the common nutritional treatments are contra-indicated. Through BSF´s registry, we have observed a growth pattern similar to but often more severe than constitutional growth delay with accelerated growth to normal height during mid- to late- teenage years.
Exercise Intolerance
Cardiolipin Abnormalities
A failure of BTHS mitochondria to make adequate amounts of tetralinoleoyl-cardiolipin, an essential lipid (fat-like molecule) for normal mitochondrial structure and energy.

3-Methylglutaconic Aciduria, Type II (MGA, Type II)(Typically a 5- to 20-fold increase in an organic acid that can be measured in urine) A result of abnormal mitochondria (the “powerhouses” or primary energy producers in cells) function. However, there have been reports of normal levels of 3-methylglutaconic acid (3MGA) in confirmed cases of BTHS.

Like many genetic disorders, Barth syndrome is quite variable among different families and sometimes even within a single sibship. Whereas at least 80% of known patients with Barth syndrome manifest all four principal diagnostic criteria at some time during childhood, any or possibly even all of the cardinal findings may be absent in a boy with a proven mutation in the Barth gene. This variability in presentation of symptoms and severity in phenotype makes Barth syndrome a difficult disorder to diagnose. In absence of a family history of related illnesses, the clinician is presented with the challenge to diagnose a child who inherits the disorder through a spontaneous mutation. The diagnosis of Barth syndrome should be considered for any child or adult found to have any one of its four cardinal clinical characteristics, and evaluation for the other diagnostic criteria should be undertaken by obtaining the following studies:
  1. Quantitative urine organic acid analysis including quantification of 3-methylglutaconic acid (Type II)
  2. Complete blood count and differential
  3. Echocardiogram
  4. Analysis of growth parameters from birth

There is no specific treatment for BTHS, but each of the individual problems can be successfully controlled, and short stature often resolves after puberty.

Resources/Support and info at BSF:
University of Mississippi Medical Center

Christopher's Story
Christopher was born with a congenital heart defect known as cardiomyopathy. At 22 months this was found to be caused by a rare X linked form of mitochondrial disease called Barth syndrome. His chances of survival were not good, and he was placed on hospice care. Much to his doctors amazement his cardiomyopathy improved. He still has many struggles including severe cyclic neutropenia and muscle weakness. He is a: living, breathing, daily reminder that miracles happen. His parents cherish every moment they have with him. His mother works hard to spread awareness about a disease she believes is severly underdiagnosed.

Contributed by MOM Kristi Pena- For more about Christoper, check out his Carepage

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