What is PDCD

Overview

Pyruvate Dehydrogenase Complex Deficiency (PDCD) is a rare disorder that disrupts an individual’s ability to convert pyruvate, which mostly comes from carbohydrates, into energy. This causes both a lack of energy and a buildup of lactic acid, which can cause damage to the brain and nervous system. Lack of research and reliable information prevents a full understanding of this disorder.

PDCD is caused by an abnormal sequence of the genes that code for one of the three components of the enzyme Pyruvate dehydrogenase complex, which the body needs to create energy from food.  The most common form of PDCD is X-linked, meaning it is carried on the 23rd chromosome. Because it is a genetic disorder, PDCD cannot be contracted or spread.  It is present from birth, although some symptoms may not present themselves until later in life. Due to its severity, many newborns do not live past their first year, although there have been a few cases of children making into adulthood, and at least two instances of adults living a relatively normal life with PDCD. Later childhood onset of the disease is usually, but not always, associated with survival into adulthood.

What PDCD does

Normally, proteins, fats, and carbohydrates are metabolized into energy by the biochemical processes in the cells of body. In the case of carbohydrates, a series of reactions convert carbohydrate to pyruvate, which is next converted to the energy-forming compound acetyl CoA by the pyruvate dehydrogenase (PDC) enzyme complex.

There are many different types of Pyruvate Dehydrogenase Complex Deficiency but all of them involve a mutation of one of the components of the PDC enzyme complex which stops it from functioning properly, depriving the body of energy.

Even though pyruvate cannot be converted to Acetyl CoA by the pyruvate dehydrogenase complex (PDC), the body still has to metabolize pyruvate in some way. Instead of breaking down pyruvate by the normal pathway, pyruvate is instead turned into lactate or lactic acid.

Symptoms

Lactic acidosis can occur in anyone and is normally the result of low oxygen in the body, like after a long, hard workout. Most should recognize the feelings that can come after: nausea, hyperventilation, lethargy, irregular heart rate, and anemia to name a few.  Most of the symptoms of PDCD are related to a lack of energy. However, children with PDCD experience many of these symptoms without exerting any physical effort at all. Simply eating certain foods or experiencing stress can be enough to bring them out. This can be hard to detect in a newborn, but it can show as poor feeding, rapid breathing, general lethargy or subtle flickering of the eyeballs. Very high levels of lactic acid cause a condition known as “lactic acidosis,” which can cause deterioration of brain structures and functions.

Raised levels of lactic acid is the normal result of the anaerobic breakdown of glucose in the tissues that occurs in any infant suffering from a lack of oxygen in the bloodstream. Therefore the presence of lactic acidosis in infants does not usually suggest PDCD. In PDCD lactic acidosis persists even when the infant has adequate oxygen in its bloodstream, and is significantly increased when the infant is fed glucose by mouth or intravenous fluids. Therefore, if feeding glucose to an infant causes a rapid increase in blood lactic acid concentration, PDCD should be considered.

Issues with neurological development:

  • Poor response to visual stimuli
  • Abnormal eye movements (rapid side-to-side “flickering” of the eyeballs)
  • Ataxia (periods of incoordination)
  • Choreoathetosis (irregular muscle spasms, uncontrollable twisting and writhing)
  • Seizures (either clonic-tonic or infantile spasms)
  • Encephalopathy (brain dysfunction)
  • Hypotonia (low muscle tone, reduced muscle strength)

Respiratory problems:

  • Dyspnea (General shortness of breath)
  • Hyperpnea (Shortness of breath which causes the individual to take deep breaths)
  • Apnea (Periods of an inablitly to breath)
  • Respiratory failure

Diagnosis

In addition to the presence of elevated lactic acid in the blood and the symptoms listed above, the diagnosis of PDCD can be confirmed by examining the 21 chromosome for an abnormal sequence in the genes that code for PDC, and by assessing the efficiency of the PDC in metabolizing pyruvate in a laboratory sample. This requires a small tissue sample usually obtained by biopsy.

Treatment

While there is no known cure for pyruvate dehydrogenase complex deficiency, it may be possible to reduce the progress of PDCD and its symptoms by a combination of diet and medical care.

Diet:   It is suggested that those with PDCD follow a ketogenic diet, which is a diet high in fats and low in carbohydrates, along with adequate protein. This forces the body to burn fats instead of carbohydrates, which limits the buildup of lactic acid. A typical ketogenic diet is made up of roughly 10% protein, 65-80% fats, with the remaining percentage of daily energy attributed to carbohydrates. As with any diet, other essential dietary needs such as vitamins and minerals must still be met.

Medical care:  Thiamine, carnitine, and lipoic acid are standard supplements used in the treatment of PDCD, as are all essential vitamins and amino-acids. Thiamine has been shown to be the most effective but all three substances are usually administered.