Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Meckel syndrome ?
    ### Response:
    Meckel syndrome is a disorder with severe signs and symptoms that affect many parts of the body. The most common features are enlarged kidneys with numerous fluid-filled cysts; an occipital encephalocele, which is a sac-like protrusion of the brain through an opening at the back of the skull; and the presence of extra fingers and toes (polydactyly).
    