Kao G F, Evancho C D, Ioffe O, Lowitt M H, Dumler J S
Department of Pathology, University of Maryland School of Medicine, Baltimore, USA.
J Cutan Pathol. 1997 Nov;24(10):604-10. doi: 10.1111/j.1600-0560.1997.tb01091.x.
The dermatologic diagnosis of Rocky Mountain spotted fever (RMSF) is often presumptive; the clinical presentation includes skin rash and febrile illness with or without a clear history of tick bite. The characteristic cutaneous manifestations include a generalized skin eruption with purpuric, blanching or non-blanching macules and papules usually involving the extremities. Although skin biopsies are often performed to confirm the diagnosis, the spectrum of cutaneous histopathology in RMSF has not been well described. We studied a series of 26 cases of RMSF, of which 10 were surgical specimens and 16 were autopsies. The microscopic changes were correlated with the duration of illness. The main histopathologic feature was lymphohistiocytic capillaritis and venulitis with extravasation of erythrocytes, edema, predominantly perivascular and some interstitial infiltrate. Leukocytoclastic vasculitis (LCV) with neutrophilic infiltrate and nuclear dust was seen in 11 of 15 (73%) specimens from involved skin. These lesions with LCV also showed notable epidermal change including basal layer vacuolar degeneration with mild dermoepidermal interface lymphocytic exocytosis. Six lesions with LCV displayed focal fibrin thrombi and capillary wall necrosis. Apoptotic keratinocytes were noted in 3 lesions with LCV. Subepidermal blister was observed in the skin lesion of an autopsied patient with LCV changes. Another lesion of a fatal case with LCV also contained features of acute neutrophilic eccrine hidradenitis. Focal small nerve twig inflammation was noted in a third autopsy case with LCV. Plasma cells were seen in 6 of 34 specimens (18%); and eosinophils were observed in 3 (9%). The subcutaneous fat contained a mild perivascular inflammation and one case revealed focal lobular neutrophilic inflammation. Immunohistologic (IH) staining using polyclonal rabbit anti-Rickettsia rickettsii demonstrated positive staining of the organisms in the affected endothelial cells in all 12 cases tested. The cutaneous histopathology of RMSF is caused by endothelial damage by the rickettsial organisms which elicit an initial lymphohistiocytic small vessel vasculitis with progression to LCV. The vasculitis in RMSF is, therefore, considered to be a form of septic vasculitis.
落基山斑疹热（RMSF）的皮肤病学诊断通常是推测性的；临床表现包括皮疹和发热性疾病，有无明确的蜱叮咬史。其特征性皮肤表现包括全身性皮疹，伴有紫癜性、可褪色或不可褪色的斑疹和丘疹，通常累及四肢。虽然常进行皮肤活检以确诊，但RMSF的皮肤组织病理学范围尚未得到充分描述。我们研究了一系列26例RMSF病例，其中10例为手术标本，16例为尸检标本。显微镜下的变化与病程相关。主要组织病理学特征是淋巴细胞-组织细胞性毛细血管炎和小静脉炎，伴有红细胞外渗、水肿，主要为血管周围和一些间质浸润。在15个受累皮肤标本中的11个（73%）可见伴有嗜中性粒细胞浸润和核尘的白细胞破碎性血管炎（LCV）。这些伴有LCV的病变还显示出明显的表皮变化，包括基底层空泡变性和轻度真皮表皮界面淋巴细胞外渗。6个伴有LCV的病变显示局灶性纤维蛋白血栓和毛细血管壁坏死。在3个伴有LCV的病变中发现了凋亡角质形成细胞。在一名有LCV变化的尸检患者的皮肤病变中观察到表皮下水疱。另一个致命病例的伴有LCV的病变还具有急性嗜中性粒细胞性小汗腺炎的特征。在第三个有LCV的尸检病例中发现局灶性小神经分支炎症。在34个标本中的6个（18%）可见浆细胞；在3个（9%）标本中观察到嗜酸性粒细胞。皮下脂肪有轻度血管周围炎症，1例显示局灶性小叶嗜中性粒细胞炎症。使用多克隆兔抗立氏立克次体抗体进行的免疫组织化学（IH）染色显示，在所有12例检测病例中，受累内皮细胞中的病原体呈阳性染色。RMSF的皮肤组织病理学是由立克次体病原体引起的内皮损伤所致，引发最初的淋巴细胞-组织细胞性小血管炎，并进展为LCV。因此，RMSF中的血管炎被认为是一种脓毒性血管炎的形式。
