Familial/Sporadic hemiplegic migraine type 2 (FHM2/SHM2) is caused by a mutation in the ATP1A2 gene. A gene is a carrier of hereditary information. All genes together are responsible for the function and appearance of the body. A gene consists of different letters, like a word. When a mutation occurs one of these letters changes and the word becomes incorrect similar to a spelling mistake. Consequently, the gene becomes illegible to the body and this might lead to disease.
The ATP1A2 gene has a vital role in normal functioning of the brain. The brain consists of neurons which interact with each other by chemical and electrical signalling. Electrical signals travel along the neurons and this leads to the release of chemicals (neurotransmitters). The ATP1A2 gene codes for a part of a sodium-potassium pump. This pump participates in the release of neurotransmitters. When this pump does not work correctly (due to a mutation) the release of neurotransmitters does not work properly.
When someone has a mutation in ATP1A2, it can be newly arisen or it can be inherited from a parent. Each child of an individual with a mutation in ATP1A2 has a 50% chance of also being affected. This is called autosomal dominant inheritance.