フェニルケトン尿症の1剖検例

An Autopsy Case of Phenylketonuria

I．はじめに

　フェニルケトン尿症（PKU）は，先天代謝障害のいわば原型としてますます注目され，最近では乳幼児期におけるスクリーニングすら要請されている反面，その病理形態学的裏付けは予想外に乏しく，Penrose（1939）^1）の最初の報告以来現在までに40例あまりにすぎず，本邦でも加藤ら（1962）^2）の1例をみるのみである^＊＊＊＊。その病理所見は，ほとんど特異な変化を認めないとするものも少なくないが，一般にはAlvord（1950）^3）の記載以来白質の変化が注目されている。しかしその白質病変はかなり多様で，議論の方向も一定せず，とくに髄鞘の形成不全か^4）5），髄鞘の崩壊か^6）をめぐつて，なお議論が続けられている。

　われわれは，臨床的にPKUと診断されていた1例を病理組織学的に検索し，おもに大脳白質に広汎な病変を見いだしたのでここに報告し，本症の病理形態学的側面を捉えようと思う。

A 37-year-old man, whose sister was afflicted with the same disease, had a normal birth but his subsequent development was severely retarded. Epileptic seizures occured since the age of 10 years, which became associated with myoclonic jerk. When admitted to the hospital at the age of 30 years, he exibited a blonde hair with lighter coloured eyes, but noabnormalities in the neurological examinations. Repeated urine tests were positive for phenylke-tonuria. At the age of 32 years, he showed spastic quadriplegia, a mild atrophy of the lower extremities, hyperactive deep reflex associated with Babinski signs and ankle clonus, that had slowly progressed for five years.

The autopsy revealed bilaterally symmetrical demyelination of subcortical white matter in lateral parieto-occipital regions.The demyelination was associated with intense gliosis and sudanophil fat deposits with preservation of U fibers. The axis cylinders showed a very considerable loss. The white matter in non-demyelinated areas and optic tracts showed widespread vacuolation (status spongiosus) associated with mild gliosis but without fat. The cortex showed mild cytoarchitectural abnormalities and immaturity of neurons. Pigment was well preserved in the substantia nigra and locus caeruleus. Secondary degeneration of pyramidal tracts was found both in the medulla and the spinal cord.

The clinico-pathologic features of this case were discussed in comparison with those in the previous references, and some theoretical considerations on the pathogenesis were made.