Mitochondrial Neurogastrointestinal Encephalopathy Disease
What else is it called?
- Mitochondrial myopathy with sensorimotor polyneuropathy, ophthalmoplegia, and pseudo-obstruction
- Mitochondrial neurogastrointestinal encephalopathy syndrome
- MNGIE disease
- MNGIE syndrome
- Myoneurogastrointestinal encephalopathy syndrome
- Oculogastrointestinal muscular dystrophy
- Polyneuropathy, ophthalmoplegia, leukoencephalopathy, and intestinal pseudo-obstruction
- Thymidine phosphorylase deficiency
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What causes it?
MNGIE disease is caused by mutations (changes) in the TYMP gene (previously known as ECGF1). This gene provides instructions for making an enzyme called thymidine phosphorylase. This enzyme breaks down thymidine (a molecule known as nucleoside which is used as a building block for DNA) into smaller molecules which helps control the level of nucleosides in cells.
In people with MNGIE disease, mutations in the TYMP gene cause the activity of thymidine phosphorylase to be greatly reduced or eliminated completed. A lack of this enzyme causes thymidine to build up in very high levels in the body. An excess of this molecule is destructive to a specific kind of DNA called mitochondrial DNA. This causes digestive and neurological problems found in MNGIE disease however it is not exactly clear how faulty mitochondrial DNA cause specific features of the disease.
How common is it?
The prevalence of MNGIE disease is unknown. About 70 people have been reported with this disorder so far.
What are the signs and symptoms?
The symptoms and the severity of the disease varies from patient to patient. Symptoms usually start before the age of 20 years but may range from 5-60 years of age. The symptoms of MNGIE include a variety of gastrointestinal (digestive/abdominal) and neurological problems.
The most common gastrointestinal symptom of MNGIE is the dysfunction of the muscles of the gastrointestinal tract (gastrointestinal dysmotility) over time.
Other gastrointestinal symptoms may include:
- Abdominal pain
- Feeling full very easily (premature satiety)
- Stomach rumblings (borborygmi)
- Difficulties swallowing (dysphagia)
- Failure of the intestines to absorb nutrients during digestion (malabsorption)
- Weight loss
- Loss of tissue and muscle mass (cachexia)
The most common neurological symptoms are:
- Dropping of the upper eyelid (ptosis)
- weakness of additional muscles around the eye gradually restricting the movements of the eyes (ophthalmoplegia)
- hearing loss
- peripheral neuropathy (damage or problems with the peripheral nervous system) symptoms of peripheral neuropathy include:
- weakness of muscles of the arms or legs
- abnormal sensations such as tingling (paraesthesia)
- burning or numbness in the arms or legs
How is it diagnosed?
MNGIE disease is diagnosed through specialised blood tests or an MRI (magnetic resonance imaging). Blood tests can show elevated levels of lactic acid. In MNGIE, MRI is used to show asymptomatic (showing no symptoms) leukoencephalopathy (disease in the brain). Alternatively, diagnosis can be confirmed through molecular genetic testing by showing specific genetic mutations linked to MNGIE disease.
Can it be treated?
Treatment for MNGIE involves treating specific symptoms present in the individual. These include management of gastrointestinal dysfunction through airway protection, medication for nausea and vomiting and nutritional support such as bolus feedings (using a syringe to deliver formula through a feeding tube). Children with MNGIE also often need special schooling arrangements as well as physical and occupational therapy to maintain mobility (movement).
Do my family need to be tested?
MNGIE disease is an inherited condition. Humans have chromosomes made up of DNA. Genes are pieces of DNA that carry the genetic information. Each chromosome may have several thousand genes. We inherit chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents.
Carriers of the condition do not have the disorder because the other gene of this pair is working normally. Parents of children with MNGIE disease are carriers.
The pattern of inheritance in this condition is autosomal recessive. This means:
When both parents are carriers, the risk to the baby in each pregnancy is
- 25% chance (1 in 4) of developing the condition
- 50% chance (1 in 2) for the baby to be a carrier of the condition
- 25% chance (1 in 4) for the baby to have two working genes and neither have the condition nor be a carrier