[A case of Hashimoto's encephalopathy successfully treated with cyclophosphamide pulse therapy]

Hashimoto's encephalopathy has been described as an autoimmune disorder which demonstrates favorable response to corticosteroid therapy. However, steroid-resistant cases which require additional treatment are frequently reported, and there is no consensus how such cases should be treated. We present a 69 years-old man, who progressed cognitive dysfunction in the past three months. Anti-thyroid and anti-NH₂ terminal of alpha-enolase antibodies were positive. Because initial corticosteroid therapy was ineffective, cyclophosphamide (CPA) pulse therapy was added, and his cognitive function was immediately improved. He had no relapse after tapering dose of corticosteroid for three years. CPA pulse therapy should be considered for steroid-resistant Hashimoto's encephalopathy.