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Pyruvate dehydrogenase deficiency


Other Names for this Disease
  • PDHC
  • Pyruvate dehydrogenase complex deficiency
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Overview



What is pyruvate dehydrogenase deficiency?

What are the signs and symptoms of pyruvate dehydrogenase deficiency?

What causes pyruvate dehydrogenase deficiency?

How is pyruvate dehydrogenase deficiency inherited?

Is genetic testing available for pyruvate dehydrogenase deficiency?

How is pyruvate dehydrogenase deficiency diagnosed?

How might pyruvate dehydrogenase deficiency be treated?


What is pyruvate dehydrogenase deficiency?

Pyruvate dehydrogenase deficiency is metabolic disorder associated with abnormal function of the mitochondria in cells, thus depriving the body of energy. Progressive neurological symptoms usually start in infancy but may be evident at birth, or in later childhood; these symptoms may include developmental delay, intermittent ataxia, poor muscle tone (hypotonia), abnormal eye movements, or seizures. Severe lethargy, poor feeding, and tachypnea (rapid breathing) commonly occur, especially during times of illness, stress, or high carbohydrate intake. Childhood-onset forms of the condition are often associated with intermittent periods of illness but normal neurological development. Prognosis is difficult to predict due to the many causes of the condition, but in most cases of neonatal and infantile onset, prognosis is described as poor. The most common form of pyruvate dehydrogenase deficiency is caused by mutations in the E1 alpha gene, and is inherited in an X-linked dominant manner; all other forms are caused by various genes and are inherited in an autosomal recessive manner. In addition to directly treating acidosis and providing alternative energy for the body, treatment typically includes dietary supplementation with thiamine, carnitine, and lipoic acids, although not all individuals respond to this therapy.[1]
Last updated: 1/4/2011

What are the signs and symptoms of pyruvate dehydrogenase deficiency?

Pyruvate dehydrogenase (PDH) deficiency can have a significant effect on fetal development, which may become apparent during late pregnancy with poor fetal weight gain and decreasing levels of estriol in the urine of the mother during pregnancy. Delivery may be complicated, and babies may have low Apgar scores. A low birth weight is common. It has been suggested that there is a characteristic abnormal appearance associated with PDH deficiency, which may include a narrow head, prominent forehead (frontal bossing), wide nasal bridge, long philtrum and flared nostrils; however, these are not seen in all individuals and these features may occur with other disorders as well. Other abnormalities that have been reported include a simian crease, short neck, slight shortening of the limbs, flexion contractures (bent fingers), pes cavus (high arched foot), club foot, ventricular septal defect, and hydronephrosis.[2]

Individuals with PDH deficiency typically develop symptoms soon after birth. In general, there are two major types of onset: metabolic and neurological. The metabolic type presents as severe lactic acidosis (too much lactate in the bloodstream). This often does not respond to treatment, thus many of the individuals with this type of onset die during the newborn period (in very few cases, the lactic acidosis has been reported to respond to high doses of thiamine). Some individuals with severe lactic acidosis have also had severe hyperammonemia (high levels of ammonia in the blood). Individuals with the neurological type typically have hypotonia (poor muscle tone), poor feeding, and lethargy, and they later develop seizures. This type typically progresses to severe mental retardation, microcephaly (small head), blindness, and spasticity with secondary contractures (damage to muscles and tendons). However, long term survival is possible and several individuals with this type have reportedly reached their teens. Between these two extremes, there is a continuous range of intermediate forms. When the metabolic abnormalities (lactic acidosis and hyperammonemia) are less severe, the onset may be delayed until later in infancy, and these individuals may have intermittent episodes of lactic acidosis, which often is brought on by an illness and is associated with cerebellar ataxia (abnormal muscle movement). Some of the individuals with primarily neurological symptoms are said to have Leigh's disease.[2]

Although PDH deficiency occurs in males and females equally, the presentation of the disease differs between them. The metabolic type, especially the severe neonatal lactic acidosis, is much more common in males; the chronic, neurological form is much more common in females.[2]
Last updated: 1/4/2011

What causes pyruvate dehydrogenase deficiency?

Pyruvate dehydrogenase (PDH) deficiency is usually caused by a deficiency of one or more enzymes or cofactors (such as thiamine) that are needed for an important chemical reaction in the cells of the body. These enzymes or cofactors are part of the pyruvate dehydrogenase complex and normally convert (or aid in converting) a chemical called pyruvate to another chemical called acetyl-coenzyme A (CoA), which is one of two important chemicals the body needs to make citrate for the cells. Because pyruvate cannot be converted to acetyl-CoA, there is too much pyruvate in the cells, which then gets used to produce more lactic acid (which is toxic in large amounts) and alanine; there is also not enough citrate being made by the body. Citrate is the first step in another important group of chemical reactions called the citric acid cycle, which then cannot proceed. The body tries to make alternate pathways to produce more acetyl-CoA, but there is still not enough energy made in the body, especially in the central nervous system (CNS). The amount of energy that is deficient depends on the amount of the enzyme that is deficient. The condition is sometimes referred to as pyruvate dehydrogenase complex (PDHC) deficiency because there is a "complex" of three enzymes normally used in the reaction; when any one or more of the enzymes needed for the above-described reaction are deficient, the condition results. The most common form of pyruvate dehydrogenase deficiency is caused by mutations in the X-linked dominant E1 alpha gene; all other causes are thought to be due to mutations in recessive genes.[3]
Last updated: 1/4/2011

How is pyruvate dehydrogenase deficiency inherited?

Pyruvate dehydrogenase deficiency is most commonly caused by mutations in the E1 alpha gene, which is located on the X chromosome (one of the sex chromosomes) and is typically inherited in an X-linked dominant manner. Dominant inheritance occurs when an abnormal gene from one parent is capable of causing disease, even though a matching gene from the other parent is normal. The abnormal gene "dominates" the gene pair.[4] Females have two X chromosomes (one from each parent) and males have one X chromosome from the mother and one Y chromosome from the father. For an X-linked dominant disorder, because one mutated gene is enough to cause the condition, both males and females can have the condition. Because males have no other copy of the X chromosome with a working gene, affected males usually have more severe disease than affected females (who have another X chromosome with a working gene).  If the father carries the abnormal X gene, all of his daughters will inherit the disease and none of his sons will have the disease. If the mother carries the abnormal X gene, there is a 50% (1 in 2) chance for each child (whether male or female) to inherit the disease.[4] The condition may also be caused by a new mutation that first appears in an affected individual, without either parent carrying an abnormal gene for the condition.

The other genes that are thought to cause pyruvate dehydrogenase deficiency appear to be inherited in an autosomal recessive manner and are not on the sex chromosomes.[3] This means that two non-working copies of the gene that is causing the condition must be present for an individual to have the condition. When an individual has an autosomal recessive condition, each of that person's parents have a non-working copy of the gene and are referred to as "carriers." When 2 carriers for the same condition are having children, there is a 25% (1 in 4) chance for each child to have the condition, a 50% (1 in 2) chance for each child to be a carrier like each of the parents, and a 25% chance for each child to not have the condition and not be a carrier.
Last updated: 1/4/2011

Is genetic testing available for pyruvate dehydrogenase deficiency?

Genetic testing is available for pyruvate dehydrogenase deficiency. GeneTests lists the names of laboratories that are performing genetic testing for pyruvate dehydrogenase deficiency. To view the contact information for the clinical laboratories conducting testing click here.

Please note: Most of the laboratories listed through GeneTests do not accept direct contact from patients and their families; therefore, if you are interested in learning more, you will need to work with a health care provider or a genetics professional.
Last updated: 1/4/2011

How is pyruvate dehydrogenase deficiency diagnosed?

The diagnosis of pyruvate dehydrogenase (PDH) deficiency may be considered in any individual with early-onset neurological disease, especially if it appears to be associated with structural abnormalities in the brain and unexplained lactic acidosis. When lactic acid (also called lactate) and pyruvate in the blood do not seem to be significantly high, an important clue to the diagnosis may be high concentrations of lactate and/or pyruvate in the cerebrospinal fluid (the fluid that surrounds the brain and spinal cord). Additionally, magnetic resonance spectroscopy (MRS) of the brain may show concentrations of lactate in the central nervous system.[2][3] Analysis of serum and urine amino acids usually shows hyperalaninemia (high levels of the amino acid alanine).[3]

When lactic acidosis is present, other disorders involving pyruvate abnormalities are part of the differential diagnosis. However, in all of these conditions, the diagnosis is based on specific laboratory tests. Specific enzyme tests have been designed which measure both the individual's overall PDH activity, as well as each separate component of the complex (because any defect in the complex may cause the condition). The vast majority of individuals with PDH deficiency are found to be deficient in the El enzyme, but abnormalities have also been detected in other components.[2]
Last updated: 1/4/2011

How might pyruvate dehydrogenase deficiency be treated?

Treatment of pyruvate dehydrogenase (PDH) deficiency rarely influences the course of the disease,[5] but goals include stimulating the pyruvate dehydrogenase complex (PDHC), providing alternative sources of energy, and preventing immediate, acute worsening of the condition. However, even with treatment, damage to the central nervous system is common.[3] Lactic acid accumulation may be lessened by giving a high fat/low carbohydrate (ketogenic) diet, but this does not alleviate the neurological symptoms, because structural damage in the brain is typically present from before birth.[5] There is some evidence that a medication called dichloroacetate may reduce the metabolic issues in some patients. The standard of care is to supplement cofactors, which are substances in the body that help the chemical reactions in the cells to occur; these include thiamine, carnitine, and lipoic acid. The individuals with PDH deficiency that respond to these cofactors (especially thiamine) usually have a better outcome. However, giving all of these cofactors to all patients with PDH deficiency is typical in order to optimize pyruvate dehydrogenase complex function.[3] Oral citrate is often used to treat acidosis.[3]
Last updated: 1/4/2011

References
  1. Richard E Frye, Paul J Benke. Pyruvate Dehydrogenase Complex Deficiency. eMedicine. November 6, 2009; http://emedicine.medscape.com/article/948360-overview. Accessed 1/1/2011.
  2. G K Brown, L J Otero, M LeGris, R M Brown. Pyruvate dehydrogenase deficiency. Journal of Medical Genetics. 1994; 31:875-879. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1016663/pdf/jmedgene00001-0059.pdf. Accessed 1/3/2011.
  3. Richard E Frye, Paul J Benke. Pyruvate dehydrogenase complex deficiency. eMedicine. November 6, 2009; http://emedicine.medscape.com/article/948360-overview. Accessed 1/3/2011.
  4. Neil K. Kaneshiro. Sex-linked dominant. MedlinePlus. April 26, 2010; http://www.nlm.nih.gov/medlineplus/ency/article/002050.htm. Accessed 1/3/2011.
  5. G K Brown, L J Otero, M LeGris, R M Brown. Pyruvate dehydrogenase deficiency. Journal of Medical Genetics. 1994; 31:875-879. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1016663/pdf/jmedgene00001-0059.pdf. Accessed 1/4/2011.