高血圧性脳内出血で発症した原発性アルドステロン症の1例

Primary Aldosteronism Presented with Intracranial Hemorrhage

I．はじめに

　原発性アルドステロン症（primary aldostero-nism；PA）は副腎球状層に腺腫あるいは過形成が生じ，アルドステロンが過剰分泌され，腎臓の遠位尿細管を介してナトリウム再吸収，カリウム（K）と水素イオン分泌が促進する結果，高血圧症，低K血症，代謝性アルカローシスを呈する疾患である．わが国では年間200〜300例が発見され，高血圧症患者の0.5％以下に認められるとされている^5）．

　従来PAのような低レニン性高血圧は血管障害の頻度が低く，比較的良性な高血圧症であるとされてきたが，最近は本態性高血圧症と比較して脳内出血を起こす確率が高いことが指摘されている^6）．ところが，脳内出血発症の症例に限らず，PAの早期診断は必ずしも容易でなく^2），再発を予防するうえでの問題となっている．

Although primary aldosteronism (PA) has been reported as a relatively benign form of hypertension andis associated with low incidence of vascular complications, recent reports indicate that PA complicated bycerebral vascular accidents is not rare. The authors reported here that a 57-year-old man was diagnosed asa case of PA 4 years after initial treatment of intracerebral hemorrhage (ICH) and hypertension.

The patient was transferred to our department for further management of his left hemiplegia and hyper-tension after surgical treatment for a putaminal ICH at the age of 53. During the first 2 years of follow-up,he did well except for an episode of transient motor weakness. Diastolic hypertension was moderatelygood, controlled by calcium antagonists and ACE inhibitors. Laboratory data was normal, and the serumpotassium levels were in the lower limits of normal. In the last 2 years, episodes of motor weakness haveincreased. He was admitted to our hospital, under the suspicion of recurrent Todd's paralysis. The serumpotassium level ranged from 1.9 to 2.1 despite administration of potassium agents. Abdominal CT scansand 131 I-scintigraphy disclosed a left adrenal tumor. Elevation of plasma aldosterone and suppression ofplasma renin were observed. The diagnosis of PA due to hypersecretion of aldosterone from an adrenaltumor was thus confirmed. We performed a total left acIrenectomy 4 weeks after his admission. Histologic-al examination showed a clear-cell type of benign adrenal adenoma. After the operation, laboratory datawere normal and ACE inhibitors were able to normalize his diastolic hypertension.

According to the literature, PA complicated by ICH is associated with a high rate of recurrence of cere-bral vascular accidents if treatment of PA is not performed. Although diagnosis of PA in the early stage isdifficult, as it was in our presented case, high suspicion of PA is essential for patients with diastolic hyper-tension and persistent hypopotassiumemia, particularly in young adults and middle-aged patients.