A Histopathologic Study of the Human Skin in the Early Stage
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Yonago Acta Medica 2017;60:186–199 Patient Report A Histopathologic Study of the Human Skin in the Early Stage After a Tick Bite: A Special Reference to Cutaneous Tissue Reaction to the Cement Substance of Tick Saliva Motoyuki Mihara Mihara Dermatology Clinic, Tottori University, 1933-1, Takao, Niimi, Okayama, 718-0003, Japan ABSTRACT Immediately after a tick attaches to the host skin, The Ixodidae family of hard ticks has cement-producing its mouthparts are inserted into the skin for feeding, and non-cement-producing species. Involved skins of followed by the secretion of saliva. One of the physi- four patients bitten by cement-producing ticks and two ologically active substances contained in the saliva is by non-cement-producing ticks were histopathologically “cement.” According to a recent paper,1 tick bites on the examined. Those of the latter two patients were also human skin in Japan are caused by the Ixodidae family studied immunohistochemically to characterize the infil- only. However not all species in the Ixodidae family pro- trating inflammatory cells. In patients with cement-pro- duce the cement substance.2 Although there are several ducing ticks, the cement substance was observed as ex- studies concerning the histopathology of the tick bite,3–9 ternal cement or outer zone of internal cement, respec- to my knowledge, there are no reports, to date, that have tively. Coagulative necrosis was present in the epidermis critically evaluated the relationship between the cement in one patient and from the epidermis to the dermis in substance and the tissue reaction of the host skin. another patient. Epidermal cells were damaged in the This paper describes two patterns of inflammatory remaining two patients. Despite these severe tissue dam- tissue reaction in the human skin in the early stage after ages, the cutaneous inflammatory reaction in all four tick bite depending on whether or not the cement sub- patients was very mild. In contrast, the patients bitten stance is produced. by non-cement-producing ticks had severe cutaneous in- flammatory reaction. In addition to caseous necrosis-like PATIENT REPORT change in the entrance site of the inserted mouthparts, Six patients with a single tick bite were examined. Skin extensive interstitial lymphohistiocytic infiltrate was of five of the patients was assessed by dermoscopy. The present diffusely from the dermis to the subcutaneous lesions were surgically excised and processed for histo- tissue. In one of the patients coagulative necrosis was pathology. Infiltrating cells of two patients (cases 5 and 6) present from the dermis to the subcutaneous tissue. Im- were immunostained with antibodies to cluster of differ- munohistochemically, the infiltrating lymphocytes were entiation antigens (CD). T-cell dominant and mixed moderately with B-cells. Case 1. A 1-year-old girl presented with a tick to Pathogenetically, the cutaneous inflammatory reaction the left abdomen, which the mother had noticed that is only mild in the skins involved by the cement-produc- morning. Clinically and dermoscopically, a tick was ing ticks, perhaps because inflammatory reaction in the confirmed on the skin (Insert in the right lower corner host skin is suppressed by antiinflammatory and immu- of Fig. 1), with a narrow erythematous halo surrounding nosuppressive substances contained in tick’s saliva in it. Histopathologically, the mouthparts of the tick were order to prevent position of their mouthparts fixed to the seen, penetrating the epidermis (Fig. 1). The mouthparts host skin from rejection of the host until finishing their were located within highly eosinophilic, amorphous, engorgement. In contrast, the cutaneous inflammatory mucoid substance which formed a tube with thick wall. reaction induced by the non-cement-producing ticks is The mucoid substance spread in a thick homogeneous severe, possibly because these ticks have no antiinflam- layer over the epidermis. Based on a description by matory and immunosuppressive substances in their sali- Chinery,10 the author considered this mucoid substance va, and because their saliva is much more injurious than to be typical external cement, as discussed later. The that of the cement-producing ticks. Corresponding author: Motoyuki Mihara, MD, PhD Key words cement substance; cutaneous inflammatory [email protected] Received 2017 May 22 reaction; histopathology; tick bite; tick saliva Accepted 2017 June 15 Abbreviations: AB, alcian blue (pH 2.5) stain; CD, cluster of dif- ferentiation; EVG, elastica van Gieson stain; HE, hematoxylin and eosin stain; PAS, periodic acid-Schiff stain 186 Histopathology of tick bite of human skin in the early stage MP CP WP Fig. 1. (case Fig. 1). Histopathology 1. and dermoscopy. Mouthparts (MP) penetrate the epidermis. They are located within conical part (CP) of the external cement which forms a tube. Wing-like part (WP) of it spreads over the epidermis. An arrow indicates serrated structures. He- matoxylin and eosin stain. Original magnifi cation: x100. Insert in the left upper corner. Magnifi ed serrated structures. Hematoxylin and eosin stain. Original magnifi cation: x200. Insert in the right lower corner. Dermoscopic feature of an attached tick. CP MP WP Fig. 2. Magnifi ed Fig. 1. A circumscribed part of the epidermis surrounded by thin arrows is much more eosinophilic than the intact parts of the epidermis.Fig. A thick 2. arrow indicates fi brin nets. CP: conical part of the external cement. MP: mouthparts. WP: wing-like part of the external cement. Hematoxylin and eosin stain. Original magnifi cation: x200. 187 M. Mihara cement substance made up of the wall of the tube was in the above-mentioned changes of the collagen fibers had a shade of eosinophilic color (Fig. 1). The inner surface been caused by certain permeable toxic agents in the of the tube, which had serrated structures, was much tick saliva which induced coagulative necrosis. In the more eosinophilic (Fig. 1). The serrated structures were epidermis, the massive epidermal cells had undergone associated with spicula of the tick’s hypostomal teeth, coagulative necrosis (Fig. 6). As a result, the feeding interlocking closely with each other (Insert in the left cavity was surrounded by coagulative necrosis from the upper corner of Fig. 1). A circumscribed part of the epidermis to the dermis. Aside from the necrotic portion epidermis just beneath the cement substance was much of the epidermis, the epidermal cells were unaltered. The more eosinophilic than the intact parts of the epider- papillary and subpapillary dermis had a homogeneous, mis (Fig. 2), and some of the epidermal cells exhibited prominently eosinophilic appearance (Fig. 6) and only coagulative necrosis. These findings suggested that the a few infiltrating cells. This appearance suggested that saliva of the cement-producing ticks contained certain these areas had undergone a peculiar type of degenera- toxic agents permeating the surrounding tissues. In the tive alteration, which probably belonged to coagulative subepidermis just beneath the tip of the mouthparts, necrosis and that it was possibly induced by permeable a cleavage was artificially formed, under which were toxic agents of the cement-producing tick saliva. Numer- band-like accumulation of fibrin nets (Fig. 2). A slight ous neutrophils infiltrated in the mid-dermis which was perivascular lymphohistiocytic infiltrate mixed with a interposed by a narrow coagulative necrosis area just few neutrophils was present in the upper dermis (Fig. beneath the feeding cavity (Fig. 7). In the entire dermis 1). The cement substance, the area involved by the per- outside this area, there was slight perivascular lympho- meable toxic agents, and the mouthparts could not be histiocytic infiltrate with a few neutrophils (Fig. 3B). In evaluated histochemically because they were lost in the the boundary area between the dermis and the subcu- remaining specimen. taneous tissue, considerable perivascular lymphohistio- Case 2. A 53-year-old woman presented with a part cytic infiltrate was present (Fig. 3B). Histochemically, of a tick body attached to the right clavicular region. the degenerative areas of the papillary and subpapillary Two days previously she had tried to remove an embed- dermis were stained strongly positive with periodic ac- ded tick with her fingers, but a part of it remained in the id-Schiff stain (PAS) before and after diastase digestion skin. On examination, there was a round erythematous (Fig. 8); negative with alcian blue (pH 2.5) stain (AB); area measuring about 10 x 10 mm, with a barely visible deep brown with phosphotungstic acid hematoxylin brown punctate structure. Dermoscopy revealed that the stain; and red with elastica van Gieson stain (EVG). The punctate structure consisted of a part of the tick mouth- dermal connective tissue around the feeding cavity could parts measuring about 0.5 mm in maximum width, with not be evaluated histochemically because the remaining external cement enveloping it (Fig. 3A). Histopathologi- specimen did not have such portions. cally, the central portion of the lesion was ulcerated and Case 3. A 54-year-old woman presented with a had a V-shaped deep cleavage containing two sectioned black dotted lesion on the right lower leg. She had mouthparts (Figs. 3B and 4A). In the step section the noticed an attached tick just one week before and re- cleavage was seen as a spindle-shaped empty space in moved it with her fingers, but the cutaneous lesion had the dermis containing several small remnants of the remained. On examination, a brown-black dotted lesion mouthparts (Fig. 4B). This kind of cleavage or empty with a surrounding narrow erythematous halo was pres- space has been referred to as “the cavity in the cement ent. Dermoscopically, a brown-black, irregularly square tube” or “feeding cavity” which was formed by collagen structure measuring about 1 x 1 mm was present (Fig. destruction.10–11 The inner surfaces of the feeding cavity 9A). Histopathologically, there was a crust consisting of showed irregularly shaped thick projections or smooth the mucoid substance and the underlying aggregated in- appearance (Fig.