Genetic testing for amyotrophic sclerosis (ALS), also called motor neuron disease, is usually restricted to patients with family members also affected by ALS, or patients who do not have a family history but have symptoms starting early, under the age of 40. With the UK's current genetic testing guidelines, many people with ALS who may have a genetic form of their disease would not be offered a genetic test, and so knowledge of this genetic cause would be missed. Hundreds of people in the UK and thousands of people worldwide could be being overlooked from accessing proper genetic advice and counseling, and potentially from accessing clinical trials or gene-based therapies on the horizon.