Pituitary Metastasis Presenting as Ischemic Pituitary Apoplexy Following Heparin-induced Thrombocytopenia

Abstract

Pituitary apoplexy (PA) typically results from infarction or hemorrhage in a pituitary adenoma, while PA in nonadenomatous pituitary gland is uncommon. Prothrombotic states have never been recognized as precipitating factors for PA. The authors report a case of an elderly female who received prophylactic fractionated heparin therapy due to sepsis, consequent rhabdomyolysis, and overt disseminated intravascular coagulation. On the seventh day of heparin therapy, she reported sudden vision loss, ptosis, diplopia, and severe headache. Severe thrombocytopenia and positive antibodies to the complex of platelet factor 4 and heparin confirmed heparin-induced thrombocytopenia type 2 (HIT). Magnetic resonance imaging disclosed a homogenous pituitary tumor mass with pronounced sphenoid sinus mucosa thickening and two hypointense zones within the tumor mass on contrast-enhanced images consistent with focal ischemic necrosis. The tumor was confirmed to be squamous cell carcinoma with no signs of necrosis. Ischemic necrosis was found within marginal pituitary tissue. This is the first reported case of ischemic PA associated with pituitary metastasis and the first case in which HIT triggered PA. Our case demonstrates that prothrombotic states such as HIT can precipitate ischemic PA. Pituitary metastasis can present with ischemic PA, but radiological features differ from those described in pituitary adenomas. Segregated low-signal intensity zones within the tumor mass on postcontrast images indicate partial infarction of the tumor, which could be a special feature of ischemic PA in pituitary metastasis and has never been described in pituitary adenomas. These are all novel findings and might enlighten the pathogenesis of PA.