ステロイド反応性の頭痛と多発脳神経炎で発症した非典型的Cogan症候群の1症例

A Case of Atypical Cogan's Syndrome with a Steroid-responsive Headache and Multiple Cranial Neuropathy as the Initial Symptoms

はじめに

　Cogan症候群（Cogan's syndrome：CS）は，非梅毒性実質性角膜炎に前庭機能障害と感音性難聴を伴う稀な炎症性疾患で，1945年にCogan¹⁾によって記載された。その後，さまざまな眼病変を伴う症例が報告され，Haynesら²⁾は，実質性角膜炎を伴うものを典型的Cogan症候群，それ以外の眼病変を伴うものを非典型的Cogan症候群（atypical Cogan's syndrome：aCS）とした。CSには多彩な全身臓器障害を伴うことが知られており，神経系の合併症も報告されている^3,4)。CSの病態については血管炎の関与が示唆されているが，障害部位の病理学的検討に乏しいこともあり，不明な点が多い。

　今回われわれは，ステロイド反応性の頭痛と両側性の多発脳神経炎で発症したaCSの患者を経験し，副鼻腔粘膜生検の病理学的検討を行った。本症例では生検が確定診断に役立ち，その病理学的所見からCSの病態を考えるうえで貴重な知見が得られたので報告する。

Abstract

　Cogan's syndrome (CS) is an autoimmune disorder characterized by non-syphilitic interstitial keratitis and progressive audiovestibular impairment.　Haynes et al. modified diagnostic criteria for patients with other ocular or vestibular symptoms and suggested this to be atypical CS.　We report the case of a 71-year-old man with atypical CS.　He was referred to our hospital with a headache, bilateral facial nerve palsy, left episcleritis and bilateral sensorineural hearing loss.　Serological test results for syphilis and antineutrophil cytoplasmic autoantibodies were negative.　Cerebral MRI revealed sinusitis and pituitary swelling.　Contrast-enhanced computed tomography (CT) of the aorta demonstrated thickening of the wall and stenosis of the aorta with pathological uptake on fluorodeoxyglucose positron emission tomography.　Biopsy of the sinus mucosa exhibited angiitis of the arterioles, capillaries, and venules.　Atypical CS was diagnosed on the basis of episcleritis, progressive sensorineural hearing loss and exclusion of other inflammatory diseases.

　Intravenous injection of 500mg/day methylprednisolone for 3 days was effective for alleviating the patient's symptoms, except for hearing loss, but the disease recurred during the tapering of prednisolone (PSL).　Combined therapy with PSL (10 mg/day) and methotrexate (6 mg/week) helped achieve remission of the disease.

　CS is causative of cranial polyneuropathy, but diagnosis of the former is not always straightforward as in the cases of cranial polyneuropathy.　It has been considered that CS is a subtype of polyarteritis nodosa (PN); however, the clinical signs and size of the affected vessels in the present patient are different from those in PN.　It is postulated that CS is a vasculitic syndrome that should be distinguishable from PN.

(Received: January 24,2011,Accepted: March 9,2011)