Homer 3 autoimmunity in subacute idiopathic cerebellar ataxia

Few adult patients present with an irreversible subacute cerebellar ataxia of unknown cause.1,2 The subacute evolution and the presence of CSF pleocytosis suggest a possible immune-mediated pathogenesis. In this study, we characterize the antigen of a new anti-Purkinje cell antibody identified in a patient with idiopathic subacute cerebellar ataxia.1,2 A 65-year-old woman presented in October 2000 with a week history of vertigo and vomiting. She denied symptoms of previous infectious disease. Neurologic examination revealed dysarthria, horizontal nystagmus, and severe limb and gait ataxia. Routine blood analysis, thyroid hormones, antineuronal antibodies (Hu, Yo, Ri, Ma1 and 2, CV2, Tr, GAD, and amphiphysin), brain MRI, colonoscopy, esophagogastroscopy, and CT of the chest and abdomen were normal or negative. CSF showed 27 lymphocytes/mm3 with a CSF IgG index of 1.4 (n < 0.7). She did not improve after treatment with steroids. At the last evaluation in June 2006, the cerebellar syndrome was unchanged with no cancer clinically evident. Immunohistochemistry was performed as described.3 Cerebellum samples from normal rats or mice and Homer 3–deficient mice (gift of Dr. Paul F. Worley) were subjected to standard immunoblot procedures.3 …