A genetic component in Chiari I malformation: Chiari 1 malformation in all five family members.

Under certain classifications, a Chiari type I (CMI) malformation can be characterized as a herniation of the cerebellar tonsils greater than 3 mm. Patients with CMI often have a smaller posterior fossa volume, which results in a smaller amount of space for the cerebellum, leading to the herniation of the cerebellar tonsils through the foramen magnum. Although inheritable factors such as posterior fossa volume can be traced to specific genes, there has not been a gene that can be attributed to directly causing CMI. However, several cases of CMI have exhibited a familial inheritance pattern. There are mixed findings regarding the exact nature of its inheritance, with some papers arguing in favor of an autosomal dominant pattern. In this case series, we detail a mother, father, and all 3 of their children diagnosed with CMI. Previous literature has not included both a mother and father with CMI.