1.2.3.1.2 Familial hemiplegic migraine type 2 (FHM2)

A 71-year-old retired postman reports his fifth lifetime episode of transient visual disturbance associated with limb symptoms. He describes a shimmering ring confined to his right eye alone, confirmed when he covered each eye in turn, which after a few minutes gives way to jagged bright lines spreading across his entire field of vision on that side. These two visual phenomena occur one after the other rather than together, and are consistently followed by heaviness and weakness of his right arm. The whole disturbance builds up gradually, unfolding over some eight minutes rather than appearing suddenly, and everything stays limited to the right side of his body throughout. His daughter has an identical history of attacks with weakness and underwent a formal specialist assessment in the past, being told she satisfied every element of the recognised criteria for the same familial disorder. Given the family history, genetic testing had already been arranged by his GP and had returned a confirmed pathogenic ATP1A2 variant.