Several clinical variants have been described including: ‘stiff-limb syndrome’, a limited form that spares the trunk [11, 12]; a cerebellar variant (SPS-Cer) where cerebellar symptoms are superimposed on the stiffness resulting in prominent gait ataxia [4], a paraneoplastic variant mostly associated with antibodies against amphiphysin or gephyrin [13, 14]; SPS with myoclonus (‘jerking-man syndrome’), associated with antibodies to glycine receptor, now synonymous with Progressive Encephalomyelitis with Rigidity and Myoclonus; and SPS with epilepsy and dystonia [15–22]. This evidence concerns the gene AMPH and stiff-person syndrome.