Gene links psychiatric illness and dementia

Neurodegenerative disorders

By Tessa Hoffman

15 Nov 2018

Neurologists should consider sending dementia patients with a strong family history of psychiatric illness for genetic counselling to test for the C9orf72 mutation, a conference has been told.

Speaking at the 11th International Conference on Frontotemporal Dementias, Dr Emma Devenney from the Brain and Mind Centre at the University of Sydney, said findings from a large Australian study suggest family history of psychiatric illness may be a predictor of the C9orf72 mutation known to cause frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS).

The study, published in the journal Neurology, involved interviews with 1,414 first and second-degree relatives of 89 patients with FTD and ALS with, and without the C9orf72 expansion.

It identified an almost five-fold (HR 4.9) higher probability of developing schizophrenia for relatives of C9orf72 carriers compared with noncarriers.

The probability of suicide and autism spectrum disorder was almost three times higher (HR 2.7) for family members of C9orf72 carriers, and this risk extended to FTD.

The findings point to a need for neurologists to broaden their thinking about which patients to refer for genetic testing, Dr Devenney told the conference.

Up until now, neurologists have only considered testing patients with a family history of neurodegenerative diseases.

“But what we suggest from this study is we should also be asking about psychiatric conditions because they seem to also predict whether or not you may have a genetic mutation,” Dr Devenney said.

“If there is a strong family history of schizophrenia or autism, that suggests those families are at risk of carrying the C972 mutation.”

Speaking to the limbic after her presentation, Dr Devenney said testing for the gene mutation could help neurologists diagnose and prognosticate in this group of patients.

“We don’t have a cure but it can help us tell them what will happen in the future, because we know different genes have slightly different prognoses [in terms of disease progression leading to disability and death].”

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