[Subacute cerebellar ataxia with amphiphysin antibody developing in a patient with follicular thyroid adenoma: a case report].

The patient was a 61-year-old woman with thyroid enlargement since her 20s. She began to fall down repeatedly towards the end of June 2015. She was admitted to our hospital in the middle of August because of difficulty in walking. Upon admission, she presented with neck tremor and was unable to maintain a sitting position due to ataxia of the trunk and limbs. We studied serum anti-neuronal antibodies and obtained a positive result for anti-amphiphysin antibody (AMPH-Ab). Cerebrospinal fluid analysis revealed elevated protein levels and IgG index. Other than the thyroid mass, a tumor was not detected. The resected thyroid specimen showed follicular adenoma. After performing immunotherapies, the cerebrospinal fluid protein levels and IgG index decreased, and her ataxia did not progress. When subacute cerebellar ataxia is suspected, studying AMPH-Ab should be considered.