ユビキチン陽性を呈する肺胞上皮細胞質内封入体を認めた剖検例

An Autopsy Case of Ubiquitin-positive Eosinophilic Intracytoplasmic Inclusion Bodies in Alveolar Epithelium

要旨

　ユビキチン(Ub)は神経疾患に出現することで注目された蛋白で，細胞分化，アポトーシス，シグナル伝達や神経機能などに重要な役割を担っている．しかし，限られた細胞にのみUbは陽性である．びまん性肺胞傷害(DAD)などに肺胞上皮細胞質内封入体が出現することが知られているが，今回これらの封入体にUbが陽性となった例を経験した．症例は急性間質性肺炎で入院した73歳男性で，急性呼吸不全で死亡し，剖検所見はDADであった．肺胞上皮細胞質内に糸状から球状の多彩な構造を示す好酸性封入体を認め，これらの封入体はUb免疫染色陽性であった．封入体は細胞傷害の最も強い形態像と見なせ，また，封入体形成に至らない細胞傷害を受けた肺胞上皮細胞質にもUbは陽性であった．以上から肺胞上皮細胞傷害とUbとの関連が示された．

Summary

　Ubiquitin(Ub)has been known to initially appear in diseases of central nervous system such as amyotrophic lateral sclerosis and others. Recently Ub has been found in the cytoplasm and nuclei of all cells and plays a key role in cell cycle, apoptosis, signal transmission, and nervous system. Ub has been microscopically found in form of inclusion bodies in the nervous system and hepatocytes. Eosinophilic intracytoplasmic inclusion bodies have been also found especially in diffuse alveolar damage(DAD)and we found that these inclusion bodies were positive for Ub in this report. A case of 73 years old, Japanese male was admitted to a hospital because of pneumonic infiltration, and finally he was diagnosed as DAD without clear course. Many inclusion bodies were found in alveolar epithelium in variable size and shape and all were immunohistochemically positive for Ub. Furthermore, small reaction products were also found in alveolar epithelial cells in form of non-inclusion bodies. These inclusion bodies have been considered to be morphological characteristics as cellular damage. The both inclusion bodies and non-inclusion bodies in alveolar epithelial cells were positive for Ub. This case is a first report as to Ub-positive inclusion bodies in alveolar epithelial cells and a correlation is suggested between alveolar epithelial cell damage and microscopic appearance of Ub.