A 9-year-old female with a history of autoimmune hypophysitis presented with progressive visual loss over the course of several months. As a result of her condition, she also had developed adrenal insufficiency, diabetes insipidus, growth hormone deficiency, and hypothyroidism. Her initial MRI showed pituitary stalk thickening (PST) with normal pituitary function except for diabetes insipidus. A follow-up MRI, taken at the time of presentation, revealed increased thickening and mild optic chiasm impingement. Cerebrospinal fluid (CSF) was negative for malignancy markers including alpha-feto-protein and hCG. A biopsy showed no signs of granulomas, abnormal histiocytes, or atypical lymphoid cells. LCH, Rosai-Dorfman disease, IgG4-related disease, lymphoma, and GCT were ruled out at this time. Based on these findings, the patient was diagnosed with idiopathic hypophysitis and started on corticosteroid therapy. Despite treatment, her visual function continued to deteriorate. A subsequent MRI revealed enlargement of the hypothalamic mass with optic nerve and chiasmal extension, suggesting a neoplasm. A second biopsy confirmed germinoma. After treatment, the mass reduced in size; however, the patient had developed bilateral optic atrophy with minimal visual recovery and field defects.

This case highlights the importance of considering suprasellar germinoma in pediatric PSLs, even when initial biopsies suggest hypophysitis. Overlapping clinical features can delay diagnosis and increase the risk of complications such as visual loss from optic atrophy. Clinicians should remain vigilant for progressive symptoms and atypical imaging unresponsive to standard therapies, as early diagnosis is crucial to prevent irreversible outcomes.