GRM5 and acute disseminated encephalomyelitis: The primary clinical manifestations include optic neuritis, transverse myelitis, brainstem demyelination, and acute disseminated encephalomyelitis.[3] Metabotropic glutamate receptor 5 (mGluR5) is a type of G-protein coupled receptors that is activated by binding to the excitatory neurotransmitter glutamate.