Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) C syndrome ?
    ### Response:
    C syndrome, also known as Opitz trigonocephaly syndrome, is characterized by trigonocephaly, severe intellectual disability, hypotonia, variable cardiac defects, redundant (extra folds of) skin, joint and limb abnormalities, and unusual facial features such as upslanted palpebral fissures (upward pointing outside corners of the eyes), epicanthal folds, depressed nasal bridge, and low-set, posteriorly rotated ears.
    