Multiple lung cysts are one of the major features of Birt-Hogg-Dubé syndrome (BHD), but little is known about their nature and pathogenesis. We report a case of a woman diagnosed with BHD lung cysts who exhibited pulmonary interstitial glycogenosis (PIG), a mesenchymal abnormality hitherto undescribed in this disease, in specimens resected at 14 and 29 years of age. Histopathologically, oval to spindle clear cells were seen in the subepithelial interstitial tissue of septal structures and the walls of the cysts. They had abundant periodic acid–Schiff-positive cytoplasmic glycogen. Immunohistochemically, these cells were positive for a few markers of mesenchymal stem cell-like lineage, including vimentin, CD44, and CD10, and negative for markers of epithelial or specific mesenchymal differentiation; these results were consistent with the reported immunophenotype of PIG cells. These PIG cells were more abundant in her specimen at age 14 years than in the second specimen from adulthood. The present case suggests that BHD lung cysts belong to a group of pulmonary developmental disorders characterized by combined PIG and alveolar simplification/cystic change. Disorders with PIG may persist until adulthood and may be of clinical and pathological significance.

中文翻译：

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Birt-Hogg-Dubé综合征相关肺囊肿中的肺间质糖原增多症：对发病机制的新见解？

多发性肺囊肿是 Birt-Hogg-Dubé 综合征 (BHD) 的主要特征之一，但对其性质和发病机制知之甚少。我们报道了一名被诊断患有 BHD 肺囊肿的女性病例，她在 14 岁和 29 岁时切除的标本中表现出肺间质糖原增多症 (PIG)，这是一种迄今为止在该疾病中尚未描述的间质异常。组织病理学上，间隔结构和囊壁的上皮下间质组织中可见椭圆形至梭形透明细胞。它们具有丰富的高碘酸希夫阳性细胞质糖原。免疫组织化学显示，这些细胞对间充质干细胞样谱系的一些标记物呈阳性，包括波形蛋白、CD44 和 CD10，而对上皮或特异性间充质分化标记物呈阴性；这些结果与报道的 PIG 细胞的免疫表型一致。在她 14 岁时的样本中，这些 PIG 细胞比第二个成年样本中的 PIG 细胞更丰富。本病例表明，BHD 肺囊肿属于一组以 PIG 和肺泡简化/囊性变为特征的肺部发育障碍。PIG 疾病可能持续到成年，并且可能具有临床和病理意义。