診断に苦慮した修飾麻疹による麻疹脳炎が疑われた1例

Suspected Measles Encephalitis Caused by Modified Measles that was Difficult to Diagnose: A Case Report

はじめに

　麻疹は，発熱，感冒症状，結膜炎，発疹と口腔内に特有のKoplik斑を呈する伝染性疾患である。合併症としては，年齢や基礎疾患によってさまざまであるが，中耳炎，肺炎，下痢や脳炎などが5～15％にみられる^1）。麻疹脳炎は発疹期から2週間以内に意識障害，痙攣で発症する^2）。

　近年，麻疹ワクチンの接種率が高まったことで，麻疹に特有の症状が軽症であったり，ほとんど出現せず，全体的に短い経過で治癒する修飾麻疹が多数発症するようになった^3）。

　今回われわれは修飾麻疹から麻疹脳炎を発症し，頭部造影MRIで左前頭頭頂葉に髄膜の濃染が認められ，典型的な麻疹脳炎とは異なり症状が亜急性に進行し，診断に苦慮した症例を経験したので報告する。

Abstract

　A 72-year-old man with subacute right upper limb palsy was diagnosed with cerebral infarction at another hospital.　However, the head magnetic resonance imaging (MRI) scans showed no abnormalities.　He was later transferred to our hospital because of cognitive dysfunctions.　Because his symptoms had gradually worsened, a second head MRI was performed on admission.　The scans showed an abnormality in the left frontal-parietal lobe, and the serum measles IgM level was elevated.　Measles encephalitis was consequently diagnosed and steroid pulse therapy was immediately initiated.　The patient recovered with no limb palsy or cognitive dysfunctions.　With widespread administration of the measles vaccine, we expect that the incidence of modified measles will increase in the future.　Hence the serum titer of the measles virus should be measured when patients with subacute meningoencephalitis of unclear origin are identitied.

(Received: April 26,2010,Accepted: June 29,2010)