Metachromatic Leukodystrophy患者の腓腹神経の微細構造

ULTRASTRUCTURAL STUDY OF A BIOPSIED SURAL NERVE IN METACHROMATIC LEUKODYSTROPHY

Ｉ．はじめに

　metachromatic leukodystrophyはarylsulfatase A活性の先天性欠損により，sulfatideのdegradationが障害され，これが種々の器官，特に神経系の白質に沈着する疾患であり，別名sulfatide lipidosisとよばれている^1）〜4）。多くの組織学的研究から，神経組織では軸索の破壊，脱髄とグリア増殖が報告され^5），異染性封入体が中枢神経，末梢神経，腎，肝，脾などに存在している。この異染性封入体は白質においてグリア細胞内外に，また時に神経細胞内に，末梢神経ではSchwann細胞と喰細胞にみられている^5）。

　最近，本疾患において末梢神経^6）7）および中枢神経^8）〜12）の電子顕微鏡的観察が行なわれている。これらを要約すると，中枢神経にみられる封入体は末梢神経のそれより複雑であり，しかも中枢神経の封入体にも相違が論じられている。すなわち，Aurebeckら^8）とMei Liu^10）の報告にはlamella構造をもつかまたは微細顆粒構造をもつ0.3〜1μ大の円形または卵円形の封入体と多数の顆粒，小胞および小体を含む被膜をもつ封入体がある。Gre—goireら^9），高畑ら^11）およびGreeneら^12）のものはそれとやや異なって，上に述べた0.3〜1μ大の円形または卵円形の封入体のほか，横縞のある角柱状構造をもつ封入体が認められている。

An electron microscopic study of the biopsied nerve of a patient with metachromatic leukodystro-phy was made. In the light microscopical study, a slight decrease of myelinated fibers, was observed and irregular whorls and ovoids of myelin and metachromatically stained inclusions were mainly present in the cytoplasm of Schwann cells.

The ultrastructural study confirmed the presence of irregular whorl and ovoids of myelin and a variety of inclusions in the cytoplasm of Schwann cells and revealed the loose pattern of myelin sheath. Most of inclusions had a definite limiting membrane and were classified as follows. A. Some inclusions had a dense lamellar structure, with stacked membranes 50 to 60 Å apart, which were concentric or par-pendicular to the limiting membrane. B. Some in-clusions had several membrane structures alike mitochondrial cristae to the parpendicular to the surface of the inclusions. C. Some inclusions had fine granules or the membrane structure of medium electron density. D. The rest was spindle-formed, in which fine granules or lamellar structures of about 100 Å periodicity were seen. Various inclu-sions were also found in the fibroblast which had been never described.

Some comparisons of these inclusions with those in the central nervous system were made. The inclusions in the peripheral nerve seemed to be differed somewhat from those encountered in the central nervous system. Some considerations of the relationship of these inclusions to the lysosome were considered.