Anti-Ma2 encephalitis in a phenotypic female with XY gonadal dysgenesis: A case report.

Anti-Ma2 encephalitis is an autoimmune disorder that typically involves the brainstem, limbic system, and diencephalon. It can be paraneoplastic and is more common in males. We describe an unusual presentation of anti-Ma2 encephalitis in a patient with an XY chromosome and a female phenotype. She experienced various neurological symptoms, including olfactory hallucinations, episodic nausea, per-ictal water drinking, and hypersomnolence, that were poorly controlled by antiseizure medications (ASMs) and immunotherapy. Brain MRI showed abnormalities in right medial temporal and frontal regions, and blood tests detected anti-Ma2 antibodies. Screening for malignancies yielded no tumors. Pelvic CT showed bilateral inguinal masses and the absence of a uterus, while genetic studies revealed an XY karyotype. Surgical removal of the masses, shown to be primitive gonads, offered temporary relief, necessitating ongoing ASMs and immunotherapy.