Encyclopedia
Childhood myocerebrohepatopathy spectrum, commonly called MCHS, is part of a group of conditions called the POLG-related disorders.
- genetic conditions
1. Introduction
The conditions in this group feature a range of similar signs and symptoms involving muscle-, nerve-, and brain-related functions. MCHS typically becomes apparent in children from a few months to 3 years old. People with this condition usually have problems with their muscles (myo-), brain (cerebro-), and liver (hepato-).
Common signs and symptoms of MCHS include muscle weakness (myopathy), developmental delay or a deterioration of intellectual function, and liver disease. Another possible sign of this condition is a toxic buildup of lactic acid in the body (lactic acidosis). Often, affected children are unable to gain weight and grow at the expected rate (failure to thrive).
Additional signs and symptoms of MCHS can include a form of kidney disease called renal tubular acidosis, inflammation of the pancreas (pancreatitis), recurrent episodes of nausea and vomiting (cyclic vomiting), or hearing loss.
2. Frequency
The prevalence of childhood myocerebrohepatopathy spectrum is unknown.
3. Causes
MCHS is caused by mutations in the POLG gene. This gene provides instructions for making one part, the alpha subunit, of a protein called polymerase gamma (pol γ). Pol γ functions in mitochondria, which are structures within cells that use oxygen to convert the energy from food into a form cells can use. Mitochondria each contain a small amount of DNA, known as mitochondrial DNA (mtDNA), which is essential for the normal function of these structures. Pol γ "reads" sequences of mtDNA and uses them as templates to produce new copies of mtDNA in a process called DNA replication.
Most POLG gene mutations change single protein building blocks (amino acids) in the alpha subunit of pol γ. These changes result in a mutated pol γ that has a reduced ability to replicate DNA. Although the mechanism is unknown, mutations in the POLG gene often result in fewer copies of mtDNA (mtDNA depletion), particularly in muscle, brain, or liver cells. MtDNA depletion causes a decrease in cellular energy, which could account for the signs and symptoms of MCHS.
4. Inheritance
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.
5. Other Names for This Condition
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MCHS
This entry is adapted from the peer-reviewed paper https://medlineplus.gov/genetics/condition/childhood-myocerebrohepatopathy-spectrum
References
- Cohen BH, Chinnery PF, Copeland WC. POLG-Related Disorders. 2010 Mar 16[updated 2018 Mar 1]. In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH,Stephens K, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): Universityof Washington, Seattle; 1993-2020. Available fromhttp://www.ncbi.nlm.nih.gov/books/NBK26471/
- Milone M, Massie R. Polymerase gamma 1 mutations: clinical correlations.Neurologist. 2010 Mar;16(2):84-91. doi: 10.1097/NRL.0b013e3181c78a89. Review.
- Moraes CT, Shanske S, Tritschler HJ, Aprille JR, Andreetta F, Bonilla E, SchonEA, DiMauro S. mtDNA depletion with variable tissue expression: a novel geneticabnormality in mitochondrial diseases. Am J Hum Genet. 1991 Mar;48(3):492-501.
- Rocher C, Taanman JW, Pierron D, Faustin B, Benard G, Rossignol R, Malgat M,Pedespan L, Letellier T. Influence of mitochondrial DNA level on cellular energy metabolism: implications for mitochondrial diseases. J Bioenerg Biomembr. 2008Apr;40(2):59-67. doi: 10.1007/s10863-008-9130-5.
- Stumpf JD, Copeland WC. Mitochondrial DNA replication and disease: insightsfrom DNA polymerase γ mutations. Cell Mol Life Sci. 2011 Jan;68(2):219-33. doi:10.1007/s00018-010-0530-4.
