ホモシスチン尿症の脳病変

NEUROPATHOLOGY OF HOMOCYSTINURIA

I．はじめに

　ホモシスチン尿症は，含硫アミノ酸代謝経路のうち，シスタチオニン合成酵素の先天的欠損によつて起こる^10）。本症はアミノ酸代謝異常のなかで，フェニルケトン尿症についで多いともいわれ^17），またはるかに稀ともいわれる^14）。症例の少なくとも半数以上で精神発達の障害がみられ^14,17），また少なからぬ例でけいれん発作を有するが，本症の脳の病理所見に関する報告は極めて少なく（第1表），知見はいまだ十分とはいえない現状である。

　アミノ酸代謝異常より数の少ないリピドーシスでの脳所見に関する報告が古くから多数あることは，storageという特異な極立つた病変のためであろう。しかし，発病者がより多く，しかも多くが器質性脳症状を示すアミノ酸代謝異常の脳病変に関する研究も重要であり，さきにわれわれはフェニルケトン尿症の脳病変につき詳細に報告したが^7），今回はホモシスチン尿症の3剖検例の脳病変を記し，あわせて文献例を集め考察した。

Neuropathological findings of three autopsied cases of homocystinuria with mental retardation were reported ; they were all male and the age were 15, 17 and 5-year-old respectively. Case 1 and 2 were siblings.

Venous thrombosis (case 1) and marked thickening of the wall of the venous vessels (case 3) in the leptomeninges were seen. Numerous perivenous bleedings in the paraventricular tissues were ob-served in case 1. Perivenous necrotic foci in case 1 and 2, and scattered perivenous necrotic foci throughout the whole white matter in case 3 were found. In case 1, there was diffuse demyelinating area in the temporal white matter. Such findings were considered to be due to circulatory disturbance in the venous system of the brain.

Diffusely distributed pathological changes of the grey matter were observed in all cases : slightly in case 2 and very slightly in the cases of 1 and 3. The nerve cells showed various kinds of de-generation (chromatolysis, shrinkage, vacuolisation and Nissl's severe cell disease). The end plate of the Ammon's horn was severely affected.

Reviewing the literatures and our cases, it was suggested that the characteristic neuropathological findings of hemocystinuria were the pathological changes due to circulatory disturbance in the brain. In addition, primary involvement of the nerve cells could be regarded as another important finding as well. Neuropathological study of homocystinuria in the cases without mental retardation remains to be done.