A previously healthy 64-year-old woman presented with a 3-day history of erythema and vesicles on the left arm and hand. She indicated that she had been scratched by a stray cat on the left forearm earlier. There is no fever or other discomfort. The initial diagnosis of cat scratch disease was considered, and a skin biopsy was performed. Five days later, she returned and the eruptions became getting worse. Meanwhile, new tender lesions had progressively appeared on her hands in the previous 2 days. Physical examination showed central crusted edematous erythematous plaques and a scratch on the left arm and hand (Fig. 1a) with multiple target-shaped erythematous papules symmetrically on her hands (Fig. 1b). Histopathological sections demonstrated exudation, crusting in epidermis, obviously edema in the superficial dermis and lymphocytes, histiocytes and scanty eosinophils infiltration around the blood vessels in dermis. PAS stain showed hyphae in the stratum corneum and hair follicles (Fig 1c). No Warthin– Starry-positive Bartonella henselae could be detected. Laboratory studies revealed leukocytosis (13.2 * 10/ L) and hypersensitive C-reactive protein 35 mg/L (normal, 0–10 mg/L). Serologic tests for HSV I/II were negative. Fungal culture showed white fluffy spread colonies and deep yellow-orange pigment on the reverse (Fig. 1d). The internal transcribed spacer regions of ribosomal DNA were sequenced and identified as Microsporum canis (M. canis). A diagnosis of erythema multiforme associated with tinea of vellus hair caused by M. canis was made. Terbinafine 250 mg/day and prednisone 0.5 mg/ kg/day with topical terbinafine cream were given as treatment. Erythema multiforme lesions had cleared 1 week later. Therefore, prednisone was withdrawn and terbinafine continued to be prescribed for 6 weeks. During 3 months of follow-up, the cutaneous lesions were wholly resolved. Erythema multiforme is a self-limited hypersensitivity skin reaction mostly caused by drug and infectious factors. The association of erythema multiforme with deep mycotic infections is relatively common. However, erythema multiforme with dermatophytosis is rare. Tinea of vellus hair is an uncommon manifestation of dermatophytosis. In a high percentage of cases of tinea of vellus hair, no hyphae are observed on the scales, the parasitism being exclusive to the hair. However, we present the first case of tinea of vellus hair, in which hyphae were found not only in the stratum corneum but also within the hair follicle by histopathology. Excoriation by a stray cat may play a role in the development of the tinea of the vellus hair, making some dermatophytes located in the stratum corneum penetrate into the hair follicle. It is important to distinguish tinea of vellus hair from Majocchi’s granuloma. Majocchi’s granuloma is a rare granulomatous folliculitis, which demonstrates

中文翻译：

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犬小孢子菌引起的毳毛癣相关的多形红斑

一名既往健康的 64 岁女性因左臂和手部出现红斑和水疱 3 天就诊。她表示，早些时候她的左前臂被一只流浪猫抓伤。没有发烧或其他不适。初步诊断为猫抓病，并进行了皮肤活检。五天后，她回来了，火山喷发越来越严重。同时，前两天她的手上逐渐出现了新的压痛病变。体格检查显示中央结痂的水肿性红斑斑块和左臂和手上的划痕（图 1a），手上有多个对称的靶状红斑丘疹（图 1b）。组织病理切片可见渗出，表皮结痂，真皮浅层和淋巴细胞明显水肿，真皮血管周围组织细胞和少量嗜酸性粒细胞浸润。PAS染色显示角质层和毛囊中有菌丝（图1c）。未检测到 Warthin-Starry 阳性巴尔通体。实验室研究显示白细胞增多 (13.2 * 10/ L) 和超敏 C 反应蛋白 35 mg/L（正常，0-10 mg/L）。HSV I/II 的血清学检测呈阴性。真菌培养显示白色蓬松的散布菌落和背面的深黄橙色色素（图 1d）。对核糖体 DNA 的内部转录间隔区进行测序并鉴定为犬小孢子菌 (M. canis)。诊断为与犬分枝杆菌引起的毫毛癣相关的多形性红斑。特比萘芬 250 毫克/天和泼尼松 0.5 毫克/公斤/天，外用特比萘芬乳膏作为治疗。1 周后多形性红斑病变已清除。因此，停用泼尼松，继续服用特比萘芬 6 周。随访3个月，皮损完全消退。多形性红斑是一种自限性过敏性皮肤反应，主要由药物和感染因素引起。多形性红斑与深部真菌感染的关联相对常见。然而，伴有皮肤癣菌病的多形性红斑很少见。毳毛癣是皮肤癣菌病的一种罕见表现。在高比例的毫毛癣病例中，鳞屑上没有观察到菌丝，寄生在毛发上是专有的。然而，我们提出了第一例毫毛癣，其中通过组织病理学不仅在角质层中而且在毛囊中发现菌丝。流浪猫的剥脱可能在毳毛的癣的发展中起作用，使位于角质层的一些皮肤癣菌渗透到毛囊中。区分毳毛癣和 Majocchi 肉芽肿很重要。Majocchi 肉芽肿是一种罕见的肉芽肿性毛囊炎，表现为