Stiff person syndrome and cerebellar ataxia associated with glutamic acid decarboxylase antibodies and type 1 diabetes: What is the link between neurological diseases and autoimmunity to the beta cell?

Stiff person syndrome is a rare CNS disorder characterized by progressive muscular rigidity (trunk muscles), with superimposed spasms. High titres of antibodies to glutamic acid decarboxylase (GAD-Ab) are present in more than 70 % of patients. Adult-onset cerebellar ataxia (CA) is the second most frequent disease associated with high titers of GAD-Ab, and characterized by an almost isolated cerebellar syndrome. Both syndromes are frequently associated with autoimmune type 1 diabetes (T1D). The immunogenetic basis of SPS is supported by the DQB1*0201 allele, a susceptibility allele for T1D. Several T1D autoantigens are related to proteins of the nervous system. The concordance of both neurological diseases with T1D and the presence of anti-GAD antibodies suggest a common aetiology.