Zota Victor, Angelis Sheryn M, Fraire Armando E, McNamee Ciaran, Kielbasa Shasta, Libraty Daniel H
Department of Pathology, Division of Infectious Disease, University of Massachusetts Medical School, Worcester, MA, USA.
J Med Case Rep. 2008 May 13;2:152. doi: 10.1186/1752-1947-2-152.
Mycobacterium avium complex (MAC) is an increasingly recognized cause of pulmonary disease in immunocompetent individuals. An acute form of MAC lung disease, MAC-associated pneumonitis, has generally been associated with the use of hot tubs. There is controversy in the literature about whether MAC-associated pneumonitis is a classic hypersensitivity pneumonitis or is a direct manifestation of mycobacterial infection.
We report the second case in the literature of MAC-associated pneumonitis not related to the use of hot tubs. The source of MAC in a 52-year-old immunocompetent patient was an intrapulmonary cyst containing numerous acid-fast bacilli. The patient developed disseminated miliary nodules throughout both lung fields. Histological examination of resected lung tissue revealed well-formed, acid-fast negative granulomas composed predominantly of CD4+ T-cells and CD68+ histiocytes. The granulomas were strongly positive for tumor necrosis factor-alpha, a pro-inflammatory cytokine.
The attempt to classify MAC-associated pneumonitis as either a classic hypersensitivity pneumonitis or a direct manifestation of mycobacterial infection is not particularly useful. Our case demonstrates that MAC-associated pneumonitis is characterized by a vigorous T-helper 1-like, pro-inflammatory, immune response to pulmonary mycobacterial infection. The immunopathology provides a rationale for clinical studies of anti-MAC therapy with the addition of anti-inflammatory agents (for example, corticosteroids) to hasten the resolution of infection and symptoms.
鸟分枝杆菌复合群（MAC）是免疫功能正常个体肺部疾病日益常见的病因。MAC肺部疾病的一种急性形式，即MAC相关性肺炎，通常与使用热水浴缸有关。关于MAC相关性肺炎是典型的过敏性肺炎还是分枝杆菌感染的直接表现，文献中存在争议。
我们报告了文献中第二例与使用热水浴缸无关的MAC相关性肺炎病例。一名52岁免疫功能正常患者的MAC来源是一个肺内囊肿，其中含有大量抗酸杆菌。患者双肺野出现弥漫性粟粒结节。切除的肺组织组织学检查显示形成良好的抗酸阴性肉芽肿，主要由CD4 + T细胞和CD68 +组织细胞组成。这些肉芽肿肿瘤坏死因子-α呈强阳性，肿瘤坏死因子-α是一种促炎细胞因子。
将MAC相关性肺炎归类为典型的过敏性肺炎或分枝杆菌感染的直接表现的尝试并不是特别有用。我们的病例表明，MAC相关性肺炎的特征是对肺部分枝杆菌感染产生强烈的类似辅助性T细胞1的促炎免疫反应。这种免疫病理学为在抗MAC治疗的临床研究中添加抗炎药物（例如皮质类固醇）以加速感染和症状的缓解提供了理论依据。
