Motor weakness and cerebellar ataxia in Sjögren syndrome--identification of antineuronal antibody: a case report.

We report here a combination of rare neurological manifestations of primary Sjögren syndrome (SS), such as motor-dominant motor weakness of peripheral origin, cerebellar ataxia and depression, in a Japanese female patient. An autoantibody in her serum and cerebrospinal fluid immunolabelled spinal motor neurons and cerebellar Purkinje cells. On Western blot, this antibody reacted with a protein of 34 kDa from the extract of spinal cord, dorsal root ganglion, or cerebellar cortex, which might correspond to motor weakness and cerebellar ataxia, respectively. The absence of its reactivity to the liver tissue indicates that this autoantibody targets an antigen represented exclusively in the neural tissues. Although it remains to be proved how autoantibodies, sometimes associated with SS, are involved in the development of clinical pictures, some of them are present in the cerebrospinal fluid and exhibit an exclusive affinity to neural tissues, which indicates its plausible link to neurological manifestations. Recognition of these antineuronal antibodies in SS will potentially provide a chance to treat these patients by removing or inactivating the antibody.