Neuropathy Ataxia and Retinitis Pigmentosa
What else is it called?
- NARP Syndrome
- Neurogenic muscle weakness, ataxia, and retinitis pigmentosa
- Neuropathy, ataxia, and retinitis pigmentos
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What causes it?
NARP syndrome is caused by a mutation to the MT-ATP6 gene. Although most of the genetic makeup is found in other areas of the body, this gene mutation is found inside the mitochondria where it harbours some of the body’s DNA. The mitochondria is known as the energy production centre of the cell. This type of DNA is commonly referred to as mtDNA. The genes found here are responsible for providing the mitochondria with information which enables it to break down molecules for energy, simple sugars and for oxygen. This gene is also responsible for providing the mitochondria with instructions to make a subpart of an enzyme called ATP synthase. Enzymes are proteins which are involved in breaking down molecules or compounds for energy. ATP synthase is involved in the production of Adenosine Triphosphate [ATP] which is the commonly referred to as the biological currency of the body, this is due to the body relying on this for an energy source.
Research still persists into the reason as to why these mutations causes these signs and symptoms, particularly with the muscle weakness and vision loss.
How common is it?
The current prevalence of NARP syndrome is unknown, this may be due to how rare this condition is. It is thought that NARP syndrome impacts 1 in every 12,000 people worldwide, with no preference for males or females or specific ethnicities.
What are the signs and symptoms?
Signs and symptoms for NARP syndrome vary greatly per person. Symptoms are first reported by young adults. Some of the more common signs and symptoms are:
- Neurological impairment
- Learning disabilities
- Hearing loss
- Intellectual impairment [Dementia]
- Muscle weakness
- Numbness and tingling in arms and or legs
- Balance and coordination problems
- Night blindness
In some cases, people can lose their vision [retinitis pigmentosa]. This eye condition causes the child or individual to eventually lose their vision.
How is it diagnosed?
Diagnosis for NARP syndrome can be difficult, a trained physician can make a diagnosis for this condition based on the signs and symptoms expressed, their family history and through genetic testing for this gene mutation. The mutation can mostly be found within white blood cells, but other tissue type testing may be a more routine option, these tissue types can be hair follicles or pieces of skin for the gene mutation. Urinalysis may also provide a diagnosis for this condition as lactate levels are usually elevated. Blood testing may also be done to test this as well or as an alternative. Muscle biopsy’s can also be an effective diagnostic tool that can show denervation [loss of nerve supply.
Other conditions such as Refsums disease and Cockayne syndrome, Ushers syndrome and Bassen- Kornweig all have similarities to NARP syndrome therefore diagnosis may be prolonged. However, with blood analysis and differentiation of the symptoms expressed, these other conditions can be removed as a possible diagnosis.
Can it be treated?
Sadly, there is no cure for NARP syndrome, treatment is usually aimed at managing the symptoms as they present. Treatment will be managed by a multidisciplinary team consisting of audiologists, eye specialists, paediatricians, cardiologists and other health care specialists. Coenzyme Q10 is one treatment option which has been proposed at high dose however, research still persists in this area.
Do my family need to be tested?
NARP syndrome is inherited by defects in the genome of the mitochondria, these genes found in the mitochondria are collectively known as mitochondrial DNA [mtDNA]. Mitochondrial DNA are structures which provide instructions to break down or convert molecules into energy. Because only the female egg contributes to the development of these mitochondria DNA’s, these can only be passed on by the female to their offspring, this is otherwise known as maternal inheritance. This type of inheritance pattern will never be passed on by males.
If you have previously had a child with NARP syndrome and go on to have further children, their New-born Screening test should be carried out within 24-48 hours of birth.