Masquerade Syndrome Presenting as Optic Neuritis and Retinitis Due to Pituitary Germinoma

Masquerade syndrome is a collective term for various ocular diseases presenting with clinical features resembling intraocular inflammation. Delays in definitive diagnosis and treatment can not only lead to irreversible vision loss but also impact the patient's prognosis regarding survival. We report the case of a 26-year-old male patient who presented with impaired vision in the right eye, which had persisted for six months; neuroretinitis was diagnosed. Although infectious neuroretinitis was suspected, tests for pathogens such as Mycobacterium tuberculosis, Toxoplasma, Toxocara, and Bartonella were all negative. Treatment with betamethasone eye drops alone resulted in a fluctuating course of improvement and worsening of the neuroretinitis. Ten months after the initial visit, the patient's headache-which had begun one month prior-worsened and was accompanied by vomiting and a pulsating sensation, leading to a consultation with our department of neurosurgery. Magnetic resonance imaging (MRI) revealed a lobulated mass extending from the right midbrain to the right thalamus, causing narrowing of the cerebral aqueduct and hydrocephalus. Four days after the neurosurgical consultation, the patient underwent endoscopic third ventriculostomy (ETV) and a brain biopsy, leading to a definitive diagnosis of germinoma. The headache improved the day after surgery, and by one month after the operation, the hydrocephalus had resolved, while neuroretinitis also showed improvement. The patient received carboplatin and etoposide (CARE) treatment in the second, third, and fourth months post-surgery, whole-ventricle radiotherapy (24 Gy/15 fractions) in the fifth and sixth months, and ifosfamide (IFO), cisplatin (CDDP), and etoposide (VP-16) (ICE) treatment in the seventh, ninth, and 11th months. No recurrence of the brain tumor has been observed since then. At the final follow-up visit five years post-surgery, the neuroretinitis had resolved. When neuroretinitis is observed in a young patient and infectious causes have been ruled out, intracranial germinoma should be considered in the differential diagnosis.