COL4A1 and COL4A2 genes encode the alpha1 and the alpha2 chains of type IV collagen, a key component of basement membranes. Mutations located in the coding sequence of COL4A1/COL4A2 genes are responsible for an autosomal dominant (AD) cerebral angiopathy that manifest in either adults, children or fetuses. The disease is COL4A1 or COL4A2-related cerebral small vessel disease (EFO_0700096). Also known as: COL4A1 or COL4A2-related cerebral angiopathy.