Brugada syndrome is inherited in an autosomal dominant manner, meaning that only one copy of the defective gene is needed to produce the syndrome. However, a person diagnosed with the condition may be the first in their family to have Brugada syndrome if it has arisen as a new mutation. The gene in which mutations are most commonly found in Brugada syndrome, known as SCN5A, is responsible for the cardiac sodium channel. Mutations in SCN5A associated with Brugada syndrome generally cause the flow of sodium ions to decrease. However, only 20% of cases of Brugada syndrome are associated with mutations in SCN5A, as in the majority of patients with Brugada syndrome genetic testing is unable to identify the genetic mutation responsible. Over 290 mutations in the SCN5A gene have been discovered to date, each altering sodium channel function in subtly different ways. This variation partially explains the differences in severity of the condition between different persons, ranging from a highly dangerous condition causing death at a young age to a benign condition that may not cause any problems at all. However, the genetics of Brugada syndrome are complex, and it is likely that the condition results from the interactions of many genes. Because of these complex interactions, some members of a family who carry a particular mutation may show evidence of Brugada syndrome while other carrying the same mutation may not, referred to as variable penetrance.