Familial/Sporadic hemiplegic migraine type 1 (FHM1/SHM1), episodic ataxia type 2 (EA2), spinocerebellar ataxia type 6 (SC6) and early infantile epileptic encephalopathy type 42 (EIEE42) are caused by a mutation in the CACNA1A 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 CACNA1A gene has a vital role in normal function 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 CACNA1A gene codes for part of a calcium channel. This channel participates in the release of neurotransmitters. When this channel does not work correctly (due to a mutation) the release of neurotransmitters does not work properly.
When someone has a mutation in CACNA1A it can be newly arisen or it can be inherited from a parent. Each child of an individual with a mutation in CACNA1A has a 50% chance of also being affected. This is called autosomal dominant inheritance.