Endocrine Abstracts

Introduction: Intracranial germ-cell tumors (GCT) are rare, occurring in less than 4% of pediatric patients. Histologically, they are divided into several types, among which germinomatous GCTs represent over 50% of cases. Depending on their location, GCTs usually present with symptoms of intracranial hypertension for pineal lesions, whereas suprasellar ones lead to visual disturbances or pituitary hormonal defects.

We present the case of a bifocal intracranial germinoma with an unusual clinical presentation of adipsic diabetes insipidus, a condition with significant morbidity and mortality.

Case report: A 19-year-old female patient was addressed to the emergency department with fatigue, dizziness and unsteady gait. She reported a rapid decline of visual function over the previous 15 days, although certain complaints (blurred vision of the right eye, considered to be due to myopia) had already been investigated 2 years earlier. Clinically, the patient was dehydrated, with normal blood pressure, but tachycardic. Homonymous left lateral hemianopsia was objectified as well as severely impaired vision (1/10 – right eye, 2/10 – left eye).

Biochemistry found severe hypernatremia – 177 mmol/l with hyperosmolality – 379 mOsm/kg and acute prerenal renal failure. Urines were normally diluted and thirst sensation was lost. Cerebral MRI revealed two lesions in the suprasellar and pineal regions with intense contrast-enhancement, compatible with GCTs. The suprasellar lesion extended up to the lateral ventricular floor.

Further hormonal evaluation revealed pan-hypopituitarism and hyperprolactinemia most likely due to stalk compression. Tumor markers (AFP and bhCG) were negative in serum, while bhCG was slightly elevated in CSF.

As the lesion was bifocal, with slightly elevated tumor markers, it was considered a germinoma. Treatment with chemotherapy and adjuvant radiotherapy was decided. The favorable response to treatment confirmed the diagnosis.

Conclusion: We report the case of a bifocal germinoma presenting as adipsic diabetes insipidus. To our knowledge, this is the case of intracranial CGT with this presentation. In our patient’s history, a period of polydipsia and polyuria was noted several months prior to diagnosis, but medical attention was not sought at the time. As the lesion expanded towards the hypothalamus, thirst sensation was lost, therefore leading to adipsic diabetes insipidus. Our case also underlines the importance of a thorough investigation of apparently benign symptoms, such as visual complaints or polyuria/polydipsia, especially when occurring simultaneously.