Mitochondrial respiratory chain complex I deficiency

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MRCID is caused by a problem in the nuclear of mitochondrial genes, which causes the protein called complex I to be made in short supply or incorrectly. By having a problem in this nuclear or mitochondrial gene the cells within the body will have a hard time converting food into energy. 

Mitochondrial diseases are thought to occur in about 1:8,500 people and this form of the disorder is the most common cause of mitochondrial disease in children. it accounts for around 30% of cases. 

MRCID can manifest at any age and the signs and symptoms are: 

• Decreased activity of Complex I 
• Loss of control of bodily movements (ataxia) 
• Failure to thrive  
• Enlarged liver (hepatomegaly)  
• Hypoglycaemia  
• Enlarged and thickened heart muscle (hypertrophic cardiomyopathy)  
• Increase lactate in the body (lactic acidosis)  
• Lethargic 
• Weak muscle tone 
• Cross eyed (strabismus) 
• Respiratory impairment  
• Involuntary rapid eye movements 

MRCID can be diagnosed using a person’s genetic medical history, their symptoms, a physical examination and take samples of their blood and urine in order to make an accurate diagnosis. 

There is an orphan drug known as alpha-tocotrienol quinone available in both Europe and the USA. However, it is used to treat leigh syndrome, which is a disorder related to MRCID.  

MCID is an autosomal recessive inherited metabolic disorder which means that for a person to inherit this disorder, they will need to inherit it from their parents. Humans are made up of 46 chromosomes and we inherit 23 chromosomes from each parent, in the form of the egg and sperm which combine to determine the characteristics of the child. Every human being has two copies of the genes which are needed in order to produce the complex I protein. If both of these genes are faulty then MCID will develop. The parents do not necessarily need to suffer from MCID they can be carriers, carriers are people who carry one faulty gene for a particular protein and they do not develop the disease because the other gene works correctly.  

In the event that both of the parents are carriers of MCID. There is a: 

• 25% chance that one of the children will be unaffected by MCID and will not be a carrier. 
• 25% chance that the child will inherit MCID.  
• 50% chance that the child will be unaffected by MCID and will be a carrier.     

References are available on request. Please contact us on 0800 652 3181 or by emailing contact@metabolicsupport.org.

Please note calls to 0800 numbers are free from UK landlines and mobiles. Calls from business lines may be charged – please check with your provider.

This information about metabolic diseases is provided by Metabolic Support UK and is intended for educational purposes only. It should not be used for diagnostic or treatment purposes.

Should you require more detailed information please contact Metabolic Support UK by email (contact@metabolicsupport.org) or by telephone ( 0800 652 3181). For specific medical information regarding a disorder or individual please contact your GP or Paediatrician. Metabolic Support UK accepts no responsibility for any errors or omissions nor does Metabolic Support UK assume any liability of any kind for the content of any information contained within this summary or any use that you may make of it.