We report on a 15-year-old girl who had presented with acute onset central diabetes insipidus at the age of 8 years; this was followed by growth failure due to acquired growth hormone deficiency. Initial magnetic resonance imaging showed a uniformly enlarged pituitary stalk and absence of posterior pituitary hyperintensity. Frequent patient examination and magnetic resonance imaging gave unchanged results until after 5 years a large hypothalamic mass and panhypopituitarism were found. Dynamic magnetic resonance imaging documented hypothalamic-pituitary vasculopathy. Histopathological examination revealed perivascular inflammatory lymphoplasmic infiltrates with no granulomatosis or necrosis and negative staining for S-100 protein, suggesting autoimmune inflammatory disease (lymphocytic infundibuloneurohypophysitis?). The response to glucocorticoid pulses (30 mg/kg per day for 3 days i.v.) was favorable. the hypothalamic mass being halved and partial anterior pituitary function recovery maintained for 2 years after the start of treatment. We suggest that long-term surveillance is needed for isolated and chronic thickening of the pituitary stalk and that dynamic magnetic resonance imaging can contribute to the demonstration of hypothalamic-pituitary vascular impairment associated with local vasculitis.