Genetic testing for peripheral neuropathy: we are entering a new era.

There are literally hundreds of different causes for peripheral neuropathy. While in most cases a decent history and a few blood tests can provide a potential cause, which often turns out be metabolic in nature (e.g diabetes, impaired glucose tolerance), in some patients a diagnosis proves elusive despite extensive investigations. This is a major problem as specific treatments depend largely on finding the underlying cause of neuropathy.

Recently it has become clear that there are patients who have neuropathy due to unknown causes who may harbour a genetic mutation that is causing the condition. This obviously has significant implications not just for the patient themselves, but also for other family members. The spectrum of genes associated with the most common form of inherited neuropathy, Charcot-Marie-Tooth disease has expanded significantly in recent years, to the point where now more than 50 genes have been identified with the condition. Genetic testing for a lot of these is difficult and time-consuming, which often means that the exact mutation remains undiscovered.

The development of new techniques in gene testing has changed all of this and there is an interesting paper in this month’s issue of JNNP which outlines this very nicely . Klein and colleagues have reported on the utility of whole exome sequencing (WES) in the investigations of patients who have a neuropathy that is thought to be genetic in origin, but where previous testing procedures have proven to be futile. The authors demonstrate that this novel genetic testing procedure may help provide a genetic diagnosis in these cases. This obviously has critical importance for the patients themselves, who would otherwise have to carry on without a clear diagnosis, and for their families for whom genetic counselling depends so much on obtaining a precise diagnosis.

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