GPHN and stiff-person syndrome: Several variants of SPS have been identified, including stiff limb syndrome, affecting one limb; a cerebellar variant characterized by cerebellar symptoms associated with rigidity and leading to pronounced gait ataxia; a paraneoplastic variant with antibodies against amphiphysin or gephyrin; an SPS with myoclonus (jerking man syndrome) also known as progressive encephalomyelitis with rigidity and myoclonus (PERM) linked to glycine receptor antibodies; and SPS presenting with epilepsy and dystonia [2].