Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) familial porencephaly ?
    ### Response:
    Familial porencephaly is part of a group of conditions called the COL4A1-related disorders. The conditions in this group have a range of signs and symptoms that involve fragile blood vessels. In familial porencephaly, fluid-filled cysts develop in the brain (porencephaly) during fetal development or soon after birth.
    