Idiopathic NBIA
Idiopathic NBIA is of unknown origin, although it is suspected to be genetic. For many families, the person diagnosed with NBIA is the first and only affected individual, so it is difficult to know whether there is a specific pattern of inheritance. It is thought that most of these cases are probably recessive because some families have more than one affected child and idiopathic NBIA is more common in families in which the parents are related, such as distant cousins. That would make it more likely that they share a recessive gene.
The symptoms are more varied because there are probably several different causes of neurodegeneration for individuals in this group. As with other forms of NBIA, the idiopathic form features early- and late-onset types. Currently, about five percent of those diagnosed with NBIA are believed to be in this group.
Clinical Diagnosis
Suspicion of NBIA usually arises when an MRI of the brain shows excessive iron accumulation, along with a movement disorder. Depending on symptoms, genetic testing is done to rule out other forms of NBIA or other genetic disorders. If all are negative, but the findings are characteristic of NBIA, then the diagnosis of Idiopathic NBIA is given until further evidence of the genetic origin or another cause is determined.
Evaluations Following Initial Diagnosis
- Neurologic examination for movement disorders, including dystonia, rigidity, spasticity and choreoathetosis, which are involuntary movements that include contractions, twisting and writhing. Walking ability and speech also are assessed.
- An eye exam to check for such problems as retinopathy (damage to the small blood vessels in the retina) and optic atrophy (the loss of some or most of the fibers of the optic nerve).
- Developmental screening, with referral for more formal testing if delay is indicated.
- Assessment to see if physical therapy, occupational therapy and/or speech therapy are warranted.
- Assessment of behavior and neuropsychiatric changes.
- Medical genetics consultation.
Management
Doctors treat patients with medication when appropriate. Also, affected individuals may need a feeding tube or other assistance to achieve adequate nutrition. Other therapies might also be warranted.
Genetics
Testing to find the gene responsible for an individual’s form of NBIA may be pursued.
Prenatal Testing
In the absence of a known genetic mutation, testing during pregnancy to assess risk is not possible.
Research
Researchers continue their search for remaining genes that cause NBIA disorders, and much progress is being made with new technology. If a new gene is found by researchers, the person’s samples will be examined to see if they have mutations and their form of NBIA identified. Affected individuals diagnosed with Idiopathic NBIA might want to participate in the TIRCON International Patient Registry.
