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Deepika vegiraju at 15:50, 8 December 2020

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== '''Alternate names''' ==
PC deficiency; Ataxia with lactic acidosis 2; Leigh necrotizing encephalopathy due to pyruvate carboxylase deficiency; Leigh syndrome due to pyruvate carboxylase deficiency.

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== '''Definition''' ==
Pyruvate carboxylase deficiency is an inherited disorder that causes [[lactic acid]] and other potentially toxic compounds to accumulate in the blood.
High levels of these substances can damage the body's organs and tissues, particularly in the [[nervous system]].

== '''Types''' ==
Researchers have identified at least three types of pyruvate carboxylase deficiency, types A, B, and C, which are distinguished by the severity of their signs and symptoms.

== '''Epidemiology''' ==
Pyruvate carboxylase deficiency is a rare condition, with an estimated incidence of 1 in 250,000 births worldwide. Type A appears to be much more common in some Algonkian Indian tribes in eastern Canada.

== '''Cause''' ==
* Mutations in the '''PC gene''' cause pyruvate carboxylase deficiency. This gene provides instructions for making an [[enzyme]] called '''pyruvate carboxylase'''. This enzyme is '''active in [[mitochondria]]''', which are the energy-producing centers within cells. It is involved in several important cellular functions, including the '''generation of glucose, a simple sugar that is the body's main energy source'''.
* Pyruvate carboxylase also plays a role in the '''formation of the protective sheath that surrounds certain nerve cells ([[myelin]]) and the production of brain chemicals called [[neurotransmitters]]''' that allow nerve cells to communicate with one another.
* '''Mutations in the PC gene reduce the amount of pyruvate carboxylase in cells or disrupt the enzyme's activity'''. The missing or altered enzyme cannot carry out its essential role in generating glucose, which '''impairs the body's ability to make energy in mitochondria'''.
* Additionally, a loss of pyruvate carboxylase allows compounds such as '''[[lactic acid]] and [[ammonia]] to build up and damage organs and tissues'''. Researchers suggest that the loss of pyruvate carboxylase function in the nervous system, particularly the role of the enzyme in [[myelin]] formation and [[neurotransmitter]] production, also contributes to the neurologic features of pyruvate carboxylase deficiency.

== '''Inheritance''' ==
[[File:Autorecessive.svg|thumb|right|Autosomal recessive inheritance, a 25% chance]]
This condition is inherited in an [[autosomal recessive]] pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

== '''Signs and symptoms''' ==
'''TypeA'''
'''Type A''', which has been identified mostly in people from North America, has severe symptoms that begin in infancy.
* Characteristic features include developmental delay and a buildup of lactic acid in the blood ([[lactic acidosis]]). Increased acidity in the blood can lead to vomiting, abdominal pain, extreme tiredness ([[fatigue]]), muscle weakness, and difficulty breathing.
* In some cases, episodes of lactic acidosis are triggered by an illness or periods without food (fasting). Children with pyruvate carboxylase deficiency type A typically survive only into infancy or early childhood.

'''TypeB'''
Pyruvate carboxylase deficiency type B has life-threatening signs and symptoms that become
apparent shortly after birth.
This form of the condition has been reported mostly in Europe, particularly France. Affected infants have severe [[lactic acidosis]], a buildup of ammonia in the blood ([[hyperammonemia]]), and liver failure.
They experience neurological problems including weak muscle tone ([[hypotonia]]), abnormal movements, [[seizures]], and [[coma]]. Infants with this form of the condition usually survive for less than 3 months after birth.

'''TypeC'''
A milder form of pyruvate carboxylase deficiency, sometimes called type C, has also been described. This type is characterized by slightly increased levels of lactic acid in the blood and minimal signs and symptoms affecting the nervous system.

== '''Diagnosis''' ==
* The diagnosis of PC deficiency is established in a proband by identification of PC enzyme deficiency in [[fibroblasts]] or [[lymphoblasts]].<ref>Wang D, De Vivo D. Pyruvate Carboxylase Deficiency. 2009 Jun 2 [Updated 2018 Mar 1]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK6852/</ref>
* In individuals with PC deficiency, fibroblast PC enzyme activity is usually less than 5% of that observed in controls.
* The diagnosis of PC deficiency can also be established in a proband by identification of biallelic pathogenic variants in PC on molecular [[genetic testing]].

== '''Treatment''' ==
[[Intravenous]] glucose-containing fluids, hydration, and correction of the [[metabolic acidosis]] are the mainstays of acute management.<ref>Wang D, De Vivo D. Pyruvate Carboxylase Deficiency. 2009 Jun 2 [Updated 2018 Mar 1]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK6852/</ref>[https://www.ncbi.nlm.nih.gov/books/NBK6852//].

Correction of biochemical abnormalities and supplementation with [[citrate]], [[aspartic acid]], and [[biotin]] may improve somatic findings but not neurologic manifestations.
Orthotopic [[liver transplantation]] may be indicated in some affected individuals.
Anaplerotic therapies such as [[triheptanoin]] show some promise, especially regarding the neurologic manifestations, but need to be further evaluated.

'''Prevention of primary manifestations:''' Parental education regarding factors that elicit a crisis and early signs of decompensation; written information on the child's disorder and appropriate emergency treatment to be carried at all times; minimization of intercurrent infections and environmental stressors; high-carbohydrate and high-protein diet with frequent feedings to prevent dependence on [[gluconeogenesis]].<ref>Wang D, De Vivo D. Pyruvate Carboxylase Deficiency. 2009 Jun 2 [Updated 2018 Mar 1]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK6852/</ref>

== '''References''' ==
<references />

{{Mitochondrial diseases}}
{{Carbohydrate metabolic pathology}}

{{DEFAULTSORT:Pyruvate Carboxylase Deficiency}}
[[Category:Autosomal recessive disorders]]
[[Category:Inborn errors of carbohydrate metabolism]]
{{rarediseases}}
{{stub}}

Pyruvate carboxylase deficiency - Revision history

Prab: CSV import

Deepika vegiraju at 15:50, 8 December 2020