ミオクローヌスと運動失調を主症状としナイアシン投与が有効であったアルコール性ペラグラ脳症が疑われた1例

A Suspected Case of Alcoholic Pellagra Encephalopathy with Marked Response to Niacin Showing Myoclonus and Ataxia as Chief Complaints

症例は30年間のアルコール多飲歴がある47歳男性。食欲不振が出現後，亜急性の経過で歩行障害が出現したが，下痢の既往はなかった。入院時には肝硬変および腹水があり，四肢および体幹の運動失調，四肢のミオクローヌス，下肢の深部腱反射低下を認めたが，明らかな意識障害や皮膚炎はなかった。肝不全用アミノ酸製剤やビタミンB1の投与は無効で，ニコチン酸アミドの投与を行ったところ，徐々に運動失調やミオクローヌスは消失した。血中ナイアシンの低下も認められ，経過を含めてアルコール性ペラグラ脳症と診断した。ペラグラは近年では極めて稀な疾患となっているが，アルコール多飲者では依然として発症することがある。アルコール性ペラグラ脳症は精神症状で初発することが多いとされているが，本例のように精神症状や下痢，皮膚炎といった3D症状がなく，ミオクローヌスや運動失調が主症状となる場合があり，診断および治療には注意が必要である。

We report a 47-year-old alcoholic man with alcoholic pellagra encephalopathy (APE) showing myoclonus and ataxia as chief complaints.He had been a heavy drinker for 30 years.He had noticed appetite loss and subsequently showed a subacutely progressive gait disturbance.He had no history of diarrhea, dementia, or dermatitis.On admission, he showed severe alcoholic liver cirrhosis with a large amount of ascites, limbs and truncal ataxia, myoclonus of the limbs and areflexia, although his consciousness was alert and there were no sign of dermatitis.Though the plasma level of ammonia was normal, we started administration of amino acids suspecting hepatic encephalopathy.Symptoms showed no improvement, and subsequent administration of thiamine was also ineffective.A decreased serum level of niacin was demonstrated.After administration of nicotinamide, the symptoms improved gradually.This patient received a diagnosis of APE.Endemic pellagra, characterized by the classical triad of dermatitis, diarrhea and dementia, is known to be caused by a dietary deficiency of the niacin, and has now become very rare in developed countries.At present, pellagra is encountered most often in patients with chronic alcoholism, which is called APE.APE patients often show only disturbance of consciousness.Although several reports has described ataxia and myoclonus in patients with APE, APE patients with myoclonus and ataxia as chief complaints have not previously been reported.On autopsy cases, central chromatolysis of neurons in the dentate nucleus of the cerebellum, gracile and cuneate nuclei, and the Clarke's column has been demonstrated.The APE patients would show myoclonus and ataxia as their first symptoms.In conclusion, we would like to emphasize that administration of niacin should be started for the treatment of chronic alcoholic patients showing myoclonus and ataxia even without the classical triads found in endemic pellagra patients.