Routine testing is not indicated, but the role of genetic factors should be discussed with all patients with amyotrophic lateral sclerosis (ALS)

Until recently, the world was populated by two types of patients with ALS: those with sporadic ALS (sALS) and those with familial ALS. The 5% with a family history needed special care and attention to help them come to terms with the double tragedy of having a devastating terminal disease and knowing that they could pass it on to their children. The other 95% could be confidently reassured that no one else in their family need consider themselves at risk. Furthermore, since there was only one ALS-determining gene, SOD1, affecting 20% of the familial cases, testing and counselling was relatively simple, and most patients had to accept that the precise cause of their disease could not yet be determined.

Rapid advances in ALS genetics in recent years, principally the discovery that approximately 10% of …