Abstract
Lymphocytic infundibulo-neurohypophysitis（LINH） is a rare disease that exhibits central diabetes
insipidus（CDI） through autoimmune mechanisms.
Importantly, LINH should be always differentiated from neoplasia such as Langerhans cell histiocytosis
and germinoma.
A 6-year-old boy presented with polyuria and polydipsia. Endocrinological investigations proved CDI.
Hypophysis MRI showed enlargement of the stalk and diffuse Gadrinium-enhancement, suggesting the diagnosis
of LINH. Hypophysis biopsy that is indispensable for the definitive diagnosis of LINH was not performed
in our patient because of its invasiveness. However, the follow up MRI revealed the improvement of the
stalk swelling in the time course, and this finding not only supported the diagnosis but also ruled out neoplastic
diseases. He was treated with DDAVP alone, and his CDI promptly dissolved. Since he lacked headache
and visual disorders, glucocorticoid treatment was not needed. Recently, serum anti-Rabphylin-3A antibody
has been reported as a useful diagnostic tool for LINH. Our patient also possessed this antibody in the
serum, strongly supporting the diagnosis.
