急性湿性皮炎

赵博

Acute Moist Dermatitis

急性湿性皮炎

作者：Erin E. Aufox, DVM; Linda A. Frank, DVM, MS, DACVD; Laura F. Grieco, DVM, MLAS University of Tennessee

翻译：胡永武（hyw12345）

校对：赵博

Acute moist dermatitis (AMD), commonly referred to as hot spots, typically results from self-inflicted trauma in response to painful or pruritic stimuli. Although AMD typically only involves surface bacterial colonization (ie overgrowth)—not true infection—lesions may progress quickly and result in folliculitis and, sometimes, furunculosis, especially without treatment.

急性湿性皮炎(AMD)，通常称为热斑，通常由疼痛或瘙痒刺激引起的自我损伤导致。尽管AMD通常只涉及表面细菌定殖（即过度增殖）——而不是真正的感染——病变可能迅速发展，并导致毛囊炎，有时还会导致疖病，尤其是在没有治疗的情况下。

Fleabite hypersensitivity is a primary inciting factor of AMD; lesions typically develop shortly after flea exposure. Other inciting factors can include ectoparasites, otitis externa, foreign bodies, irritating substances, and skin diseases that result from allergic dermatitis. In dogs, AMD can occur in both sexes and all ages and breeds, with male dogs <4 years and certain breeds (eg, golden retrievers, German shepherd dogs, collies, Saint Bernards) overrepresented. Dogs with heavy and dense undercoats are more susceptible to developing hot spots as a result of increased environmental temperatures and slow drying of the coat due to lack of proper ventilation, which can result in conditions that are favorable for bacterial overgrowth.

跳蚤过敏是AMD的主要诱发因素；通常在接触跳蚤后不久发生病变。其他诱发因素包括外寄生虫、外耳炎、异物、刺激物和过敏性皮炎导致的皮肤病。在犬中，AMD可发生在所有性别、年龄和品种中，小于4岁的雄性犬和某些品种（如金毛巡回犬、德国牧羊犬、柯利犬、圣伯纳犬）好发。被毛厚密的犬更易出现热斑，由于环境温度升高或缺乏适当的通风使得被毛干燥缓慢，这可导致有利于细菌过度增殖的条件。

History & Clinical Signs

病史和临床症状

Patients with AMD are typically presented subsequent to sudden onset of intense pruritus localized to one area of the body. Owners often report that no lesions existed hours prior to presentation. Patients with AMD may not receive regular or adequate flea preventive, and flea hypersensitivity is common. Typical lesion locations include the caudal dorsum and other areas the patient can reach with its mouth (Figure 1). In addition, lesions may be present on the lateral face under the pinnae and rostral to the neck. Lesions may be flat, moist, and exudative, with erosion and/or ulceration in the center. The patient’s hair is often matted, which can inhibit accurate visual examination of the lesion until after the area is clipped. Bacteria typically colonize the surface of AMD lesions, and superficial or deep pyoderma may be present in some cases. Satellite lesions adjacent to the clipped primary lesion may be suggestive of folliculitis or furunculosis (Figures 2 and 3). Lesions on the lateral face (made by scratching instead of licking or chewing) appear clinically similar to classic superficial hot spots but have often developed into deep pyodermas by the time they are evaluated by a clinician. Recognizing when AMD lesions are complicated by folliculitis or furunculosis can lead the clinician to alter recommended therapy (eg, length and frequency of topical treatment, oral antibiotic therapy, bacterial culture and susceptibility testing) and thus improve clinical outcomes.

AMD患犬通常表现为突然出现局限于身体某一个区域的强烈瘙痒。主人经常反映在就诊前的数小时并不存在病变。AMD患犬可能未接受定期或充分的跳蚤预防，跳蚤过敏是常见的。典型的病变部位包括背部尾端和患犬可用嘴触及的其他身体区域（图1）。此外，病变可出现在耳下面部侧面和颈腹侧。病变部位可能平坦、潮湿、有渗出，中央伴有糜烂和（或）溃疡。患犬的毛发经常打结，这会阻碍对病变的准确判断，直到剃除该区域的毛发。细菌通常定植于AMD病变表面，部分病例可出现浅表或深层脓皮病。剃毛后可见原发病变相邻的卫星病变，可提示毛囊炎或疖病（图2、3）。脸部侧面的病变（通过搔抓而不是舔舐或啃咬造成）在临床上与典型的浅表热斑相似，但在临床医生评价时通常已发展为深层脓皮病。当意识到AMD病变并发毛囊炎或疖病时，临床医生可改变推荐的治疗方案（如局部治疗的时长和频率、口服抗生素治疗、细菌培养和药敏试验），从而提高临床预后。

FIGURE 1 AMD on the caudal dorsum of a German shepherd dog; matted hair makes visualization of the lesion difficult.

图1 德国牧羊犬背部尾端的AMD，毛发打结是病变难以显示。

FIGURE 2 AMD secondary to otitis externa at the base of the ear. The lesion has been clipped, and satellite lesions (arrow) are evident.

图2 继发于外耳炎的耳根部AMD。病变已剃毛，卫星病变（箭头处）明显。

FIGURE 3 Clipped lesion of the dog in Figure 1. Satellite lesions (arrow) indicate folliculitis or furunculosis, not surface colonization (ie, overgrowth).

图3 图1患犬剃毛后的病变。卫星病变（箭头处）显示毛囊炎或疖病，不是表面定植（即过度生长）。

Diagnosis

诊断

Diagnosis of AMD should be based on patient history, clinical signs, and elimination of other differential diagnoses (eg, folliculitis and furunculosis, acral lick dermatitis [Figure 4], dermatophytosis, localized demodicosis, neoplasia, calcinosis cutis). Impression cytology of AMD lesions, obtained by squeezing the lesion and applying a glass slide to the surface, can reveal numerous neutrophils, extracellular cocci, and, occasionally, bacilli. Intracellular bacteria may also be present in cases of folliculitis or furunculosis. If indicated, a culture can be obtained from these lesions by first cleaning the surface with chlorhexidine solution and rinsing with sterile water to remove the surface bacteria and oral flora, then rubbing a sterile culturette on the surface of the lesion after squeezing. Similar to what is found in cases of superficial pyoderma, Staphylococcus pseudintermedius is typically isolated from AMD lesions. Histopathology is not commonly performed when AMD is suspected but can be used to rule out differential diagnoses for persistent lesions and confirm cases of folliculitis or furunculosis. In a study of 44 dogs with AMD, 54% of dogs had epithelial necrosis or ulceration with superficial neutrophilic (± eosinophilic) dermatitis and edema and 45% had evidence of folliculitis and/or furunculosis regardless of location. An earlier histopathologic study revealed similar results.

AMD的诊断应基于患犬病史、临床症状和排除其他鉴别诊断（如毛囊炎和疖病、肢端舔舐性皮炎[图4]、皮肤癣菌病、局部蠕形螨病、肿瘤、皮肤钙质沉积症）。AMD病变的压片细胞学，通过挤压病变并在表面用载玻片获得样本，可发现大量中性粒细胞、细胞外球菌，偶见杆菌。毛囊炎或疖病病例也可出现细胞内细菌。如有显示，可先用氯己定溶液清洁这些病变表面，并用无菌水冲洗，清除表面细菌和口腔菌群，随后挤压病变后，在病变表面蹭取无菌培养物。与浅表脓皮病病例中发现的相似，通常从AMD病变中分离出假中间型葡萄球菌。当怀疑AMD时，不常进行组织病理学检查，但组织病理学检查可用于排除持续性病变的鉴别诊断，并确认毛囊炎或疖病病例。在一项44只AMD患犬的研究中，不区分病变部位的情况下，54%的犬出现表皮坏死或溃疡伴浅表中性粒细胞性（±嗜酸性粒细胞）皮炎和水肿，45%的犬出现毛囊炎和/或疖病。早期的组织病理学研究显示了相似的结果。

FIGURE 4 Acral lick dermatitis of the thoracic limb. Fibrosis indicates this is not an acute lesion and should not be confused with AMD.

图4 胸部肢端舔舐性皮炎，纤维化表明这不是急性病变，不应与AMD混淆。

Treatment & Management

治疗和管理

Treatment of AMD should begin with clipping the hair of the affected area, taking care to prevent further trauma to the skin. Clipping should be performed beyond the visibly affected margin, as lesions often extend into the haired skin and can be difficult to visualize. Once the area is clipped, the area around the primary lesion should be examined to locate satellite lesions. Folliculitis or furunculosis is likely when satellite lesions are present and may necessitate the need for systemic antibiotics. The affected area should then be cleaned with a topical biocidal solution (eg, 2% chlorhexidine solution). If lesions are infected based on cytologic findings, topical treatment (eg, 2% chlorhexidine solution, antimicrobial spray or mousse containing chlorhexidine or ethyl lactate) should be used twice daily until lesions resolve. Medicated shampoos can be used alone if clipping the hair is not possible, although treatment failure may result. Systemic antibiotics are indicated if topical therapy does not resolve the infection or if areas are difficult to treat topically (eg, when infection extends into skin covered in dense hair). As with generalized pyoderma, empiric therapy should be based on typical susceptibility patterns of S pseudintermedius; amoxicillin or penicillins should be avoided due to the prevalence of β- lactamase–mediated acquired resistance to these antibiotics found in S pseudintermedius isolates. Cephalexin (22-30 mg/kg q12h) is favored instead. Cefpodoxime (5-10 mg/kg q24h), a third-generation cephalosporin, has a similar spectrum of activity against Staphylococcus spp as compared with cephalexin and is often used in smaller animals to enable appropriate administration. Clindamycin can also be used empirically; however, resistance to this antimicrobial may occur. Antibiotics should be prescribed for an appropriate length of time, just as with other presentations of folliculitis or furunculosis. The standard course of therapy is typically 3 to 4 weeks (continued 1 week past clinical resolution) for superficial infections and 6 to 8 weeks (continued 2 weeks past clinical resolution) for deeper lesions.

AMD的治疗应从剃除病变部位的毛发开始，注意防止皮肤进一步创伤。剃毛应在可见病变边缘之外进行，因为病变通常延伸至有毛发的皮肤，并且可能难以发现。剃除病变区域毛发后，应检查原发病变周围的区域，以查找卫星病灶。当存在卫星病灶时，可能出现毛囊炎或疖病，可能需要全身抗生素治疗。然后应使用外部抗菌液（如2%氯己定溶液）清洁病变区域。如果根据细胞学检查发现病变感染，应使用外部治疗（如2%氯己定溶液、含氯己定或乳酸乙酯的抗微生物喷雾或摩丝），每日两次，直至病变消退。如果不能剃除毛发，可以单独使用药物香波，但可能导致治疗失败。如果外部治疗无法解决感染或病变区域难以进行外部治疗（如当感染延伸至致密毛发覆盖的皮肤时），则适合使用全身性抗生素。与全身性脓皮病一样，经验性治疗应以假中间型葡萄球菌的典型药物敏感模式为基础；由于在假中间型葡萄球菌分离株中普遍存在对β-内酰胺类抗生素的获得性耐药，因此应避免使用阿莫西林或青霉素。更倾向使用头孢氨苄(22-30 mg/kg q12h)。头孢泊肟(5-10 mg/kg q24h)是第三代头孢菌素，与头孢氨苄对葡萄球菌属的抗菌谱相似，为了方便给药通常用于体型较小的动物。克林霉素也可以经验性使用，但可能产生对该抗生素的耐药性。与治疗其他毛囊炎或疖病一样应开具适当时长的抗生素处方。浅表感染的标准疗程通常为3-4周（临床症状消失后持续1周），深层病变6-8周（临床症状消失后持续2周）。

Antipruritic medications and, for some patients, an Elizabethan collar are also indicated, as selftrauma is key in lesion creation and perpetuation. A short course (ie, 3 days to 2 weeks) of anti- inflammatory prednisone or prednisolone (0.5-1.1 mg/kg) is recommended because fleabite hypersensitivity is often present and typically steroid responsive. Antimicrobial medications should be continued beyond discontinuation of steroids, as steroids can decrease lesion inflammation and obfuscate whether infection is truly resolved. Continuing antimicrobial medication until the skin has completely normalized (for topical medications) or is past clinical resolution (for systemic antibiotics) should help prevent relapse and recurrence. Other antipruritic options include labeled doses of oclacitinib and injectable caninized IL-31 monoclonal antibody. It is the authors’ opinion that potent topical steroids (eg, betamethasone, isoflupredone, triamcinolone) with or without topical antibiotics (eg, gentamicin, neomycin) should be avoided when treating AMD. Topical steroids may enhance bacterial growth or decrease localized antimicrobial defenses; often contain alcohol when formulated as a solution, which stings when applied to ulcerative lesions; and can counteract the patient’s local healing and immune responses, which can delay healing and perpetuate and exacerbate localized alopecia. In addition, the potential adverse effects of topical steroids— including iatrogenic Cushing’s disease, skin fragility, focal or generalized alopecia, and calcinosis cutis—may not be fully understood by pet owners, which can lead to frequent and indiscriminate use of these products, further complicate cases, and prolong patient morbidity.

因为自损是病变形成和持续存在的关键，也适合给予止痒药，或对一些患犬佩戴伊丽莎白圈。推荐短期（即3天至2周）使用抗炎剂量的泼尼松或泼尼松龙(0.5-1.1 mg/kg)，因为通常存在跳蚤过敏反应，且通常对类固醇有反应。停用类固醇后应继续使用抗菌药物，因为类固醇可减少病变炎症，却使得感染是否真正消退模糊不清。应继续使用抗菌药物，直至皮肤完全恢复正常（对于外用药物）或临床症状消失之后（对于全身性抗生素），有助于阻止恢复原状和预防复发。其他止痒选择包括标签剂量的奥拉替尼和犬源IL-31单克隆抗体注射剂。作者认为在治疗AMD时应避免外用类固醇（如倍他米松、异氟泼尼松、曲安奈德），包括单独使用或与外用抗生素（例如，庆大霉素、新霉素）联合。外用类固醇可增加细菌增殖或降低局部抗菌防御；其配制溶液通常含有酒精，用于溃疡性病变时会有刺痛；并可抵制患犬局部愈合和免疫反应，可延迟愈合，并恶化及局部永久脱毛。此外，外用类固醇的潜在不良反应—包括医源性库兴病、皮肤脆弱、局灶性或全身性脱毛和皮肤钙质沉积—宠物主人可能无法完全了解，这可能导致频繁使用和随意使用这些产品，使病例进一步复杂化，并延长患犬疾病状态。

Prevention of AMD recurrence requires identifying and addressing the underlying cause. Because fleabite hypersensitivity is commonly associated with AMD, clinicians should ensure all pets in the household are receiving a consistent, high-quality flea preventive. Patients with AMD on the lateral face should be assessed for otitis externa. Once a patient is diagnosed with AMD, a recheck examination should be performed 3 to 4 weeks after the initial visit, thus helping to ensure clinical resolution and determination of when antimicrobial therapy can be discontinued.

预防AMD复发需要确定并设法解决潜在病因。由于跳蚤叮咬过敏通常与AMD相关，临床医生应确保家中所有宠物一并接受连续的、高质量的跳蚤预防。应对脸侧AMD的患者进行外耳炎评估。一旦患犬被诊断为AMD，应在初诊后3-4周进行复查，从而有助于确保临床症状消失并确定何时可以停止抗菌治疗。

Conclusion

总结

AMD, like most dermatologic conditions, is not imminently life-threatening but can result in significant patient discomfort. Prevention of this condition can improve patient quality of life. Regular administration of high-quality ectoparasite control and vigilant monitoring and investigation of pruritus can be key to prevention of AMD.

AMD与大多数皮肤病一样，不会立即危及生命，但可导致患犬明显不适。预防这种情况可以提高患犬的生活质量。定期给予高质量的体外驱虫药并密切监测和评估瘙痒程度可能是预防AMD的关键。

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