Objective: To learn if oral steroid treatment can alter the signs of primary progressive aphasia (PPA). Many patients with PPA have had a vasectomy and there is a possible link between vasectomy and autoimmune diseases. If PPA is, at least in part, an autoimmune disease, patients might improve with immunosuppressant treatment. Design: Case report. Setting: Cognitive and memory clinic. Patient: A 68-year-old right-handed man with a 2.5-year history of progressive speech impairment who had a vasectomy 25 years prior. Results: Examination revealed that he had a nonfluent aphasia with intact repetition and comprehension. Before and during oral prednisone treatment, he was assessed for speech fluency, naming, and episodic and working memory. All assessments except episodic memory showed a dramatic improvement. On reassessment 1 month after discontinuing treatment, the patient's performance on cognitive testing had regressed toward baseline. Conclusions: Although this patient's improvement with steroid treatment provides support for the postulate that PPA might be a treatable autoimmune disease, future placebo-controlled trials are needed before conclusions can be drawn. ©2008 American Medical Association. All rights reserved.