Abstract
Anti-N-methyl-D-aspartate receptor encephalitis frequently presents with isolated psychiatric symptoms indistinguishable from primary psychosis, delaying diagnosis. The authors have described a previously healthy 35-year-old woman admitted with abrupt first-episode psychosis, who (within 48 hours and without seizures, movement disorder, or altered consciousness) developed a true aphasic syndrome, fluctuating output with semantic and phonemic paraphasias and intermittent mutism, distinct from the disorganized speech of primary psychosis. The emergence of focal language disturbance prompted neurologic evaluation. Brain magnetic resonance imaging was unremarkable; cerebrospinal fluid showed lymphocytic pleocytosis, elevated protein, and a raised immunoglobulin G index, with anti-N-methyl-D-aspartate receptor immunoglobulin G strongly positive in cerebrospinal fluid. Pelvic imaging identified an ovarian teratoma, which was resected. First-line immunotherapy (intravenous methylprednisolone and immunoglobulin) followed by plasma exchange, with short-term antipsychotic treatment, achieved sustained remission. Serial neuropsychological assessment over 18 months documented a heterogeneous recovery trajectory: early, near-complete recovery of graphomotor speed and verbal consolidation, slower recovery of associative and working-memory functions, and verbal working memory persisting as the most stable residual deficit. This case showed that rapidly evolving aphasia, distinguished at the bedside from schizophasia, can localize an autoimmune process beyond any primary psychiatric differential and trigger the workup that secures the diagnosis.