Unknown: Biopsy of a persistent pruritic papule Unknown: Biopsy of a persistent pruritic papule on the back of a 75-year-old manon the back of a 75-year-old man Stephanie A OrtmanStephanie A Ortman11, Christopher Huerter, Christopher Huerter11, Erica , Erica ReinigReinig22, Daniel Albertson, Daniel Albertson22, Deba P Sarma, Deba P Sarma22

Dermatology Online Journal 17 (3): 11Dermatology Online Journal 17 (3): 11

1. Department of Dermatology1. Department of Dermatology2. Department of Pathology2. Department of PathologyCreighton University Medical Center, Omaha, Nebraska. Creighton University Medical Center, Omaha, Nebraska. debasarma@creighton.edu debasarma@creighton.edu

Figure 1

Figure 2

These are the microscopic images from a biopsy These are the microscopic images from a biopsy of a 5 mm pruritic papule that was present for six of a 5 mm pruritic papule that was present for six months on the back of a 75-year-old man. The months on the back of a 75-year-old man. The man is otherwise healthy. He goes hunting man is otherwise healthy. He goes hunting frequently.frequently.

What is the diagnosis?What is the diagnosis?

Answer: Answer: Tick-bite dermatitis Tick-bite dermatitis

Figure 1. In the center of the biopsy, there is a Figure 1. In the center of the biopsy, there is a downward epidermal tunnel containing keratin downward epidermal tunnel containing keratin material. In the deep part, the thick hyaline material. In the deep part, the thick hyaline structure (black arrows) represents the chitinous structure (black arrows) represents the chitinous wall of the mouthpart (hypostome) of a tick.wall of the mouthpart (hypostome) of a tick.

Figure 2. In higher magnification: within the Figure 2. In higher magnification: within the chitinous wall shows several barb-like projections chitinous wall shows several barb-like projections (green arrows) that serve as anchor during (green arrows) that serve as anchor during feeding.Note the tick mouthparts in the dermis. feeding.Note the tick mouthparts in the dermis.

Figures 1 and 2 show remnants of the tick Figures 1 and 2 show remnants of the tick hypostome (mouth part) with thick chitinous wall as hypostome (mouth part) with thick chitinous wall as well as several sharp barb-like projections (green well as several sharp barb-like projections (green arrows in Figure 2) on the hypostome that serve to arrows in Figure 2) on the hypostome that serve to anchor the tick during feeding.anchor the tick during feeding.

DiscussionDiscussion Ticks are ectoparasitic arachnids that survive by a process Ticks are ectoparasitic arachnids that survive by a process

of hematophagy in which they attach to a host and feed off of hematophagy in which they attach to a host and feed off the host’s blood. Often found in tall grass located in wooded the host’s blood. Often found in tall grass located in wooded or forested regions, a tick will attach to its host by inserting or forested regions, a tick will attach to its host by inserting its cutting mandibles, known as chelicerae, and feeding its cutting mandibles, known as chelicerae, and feeding tube, known as a hypostome, into the skin of the host. tube, known as a hypostome, into the skin of the host. Covered with sharp barbs, the hypostome anchors the Covered with sharp barbs, the hypostome anchors the mouth firmly in place while the tick feeds for a few hours to mouth firmly in place while the tick feeds for a few hours to several days before detaching [several days before detaching [11, , 22]. Once it has finished ]. Once it has finished feeding and detaches from the host, a female tick will find a feeding and detaches from the host, a female tick will find a mate and lay thousands of eggs.mate and lay thousands of eggs.

Classified by body type, ticks can be divided into two main Classified by body type, ticks can be divided into two main families, the families, the IxodidaeIxodidae, otherwise known as hard-bodied , otherwise known as hard-bodied ticks, and the ticks, and the ArgasidaeArgasidae, or soft-bodied ticks [, or soft-bodied ticks [33]. Commonly ]. Commonly known hard ticks include those in the known hard ticks include those in the DermacentorDermacentor, , AmblyommaAmblyomma, and , and IxodesIxodes genera, whereas soft-bodied ticks genera, whereas soft-bodied ticks include those in the include those in the OrnithodorosOrnithodoros genus. Hard-bodied ticks genus. Hard-bodied ticks have visible anterior mouthparts and a hard dorsal plate have visible anterior mouthparts and a hard dorsal plate known as a scutum. This group of ticks is also known for known as a scutum. This group of ticks is also known for attaching to a different host for each phase of the life cycle, attaching to a different host for each phase of the life cycle, from larva to nymph to adult. Soft-bodied ticks, on the from larva to nymph to adult. Soft-bodied ticks, on the other hand, are characterized by retroverted mouthparts other hand, are characterized by retroverted mouthparts and lack a scutum.and lack a scutum.

Although hard ticks are more commonly associated with Although hard ticks are more commonly associated with disease transmission, both hard and soft ticks are important disease transmission, both hard and soft ticks are important vectors of disease and together they transmit a wide vectors of disease and together they transmit a wide variety of pathogens, including bacteria, protozoa, and variety of pathogens, including bacteria, protozoa, and viruses [viruses [11, , 22]. Figures 1 and 2 show a remnant of the tick ]. Figures 1 and 2 show a remnant of the tick hypostome that pierces the skin during feeding, as well as hypostome that pierces the skin during feeding, as well as several anchoring barbs. Whether this remnant belongs to a several anchoring barbs. Whether this remnant belongs to a hard or soft tick cannot be unequivocally determined hard or soft tick cannot be unequivocally determined because the mouthparts of hard and soft ticks are similar [because the mouthparts of hard and soft ticks are similar [33]. The two families of ticks can usually be distinguished by ]. The two families of ticks can usually be distinguished by examining the intact body of the tick for the presence or examining the intact body of the tick for the presence or absence of a scutum. The only part of a tick that may be absence of a scutum. The only part of a tick that may be seen in a skin biopsy is the mouthpart, hypostome.seen in a skin biopsy is the mouthpart, hypostome.

Whereas hard ticks feed for extended periods up to several Whereas hard ticks feed for extended periods up to several days or weeks and can grow to accommodate large days or weeks and can grow to accommodate large volumes of ingested blood, soft ticks feed more rapidly, on volumes of ingested blood, soft ticks feed more rapidly, on the order of several minutes to days. This has important the order of several minutes to days. This has important implications in terms of the spread of disease. For example, implications in terms of the spread of disease. For example, Ixodes scapularisIxodes scapularis requires 24 to 48 hours of feeding time requires 24 to 48 hours of feeding time before before Borrelia burgdorferiBorrelia burgdorferi, the causative agent of Lyme , the causative agent of Lyme disease, can be transmitted whereas disease, can be transmitted whereas OrnithodorosOrnithodoros requires requires less than an hour to transmit the spirochete that causes less than an hour to transmit the spirochete that causes relapsing fever. Thus, prompt removal or an attached tick is relapsing fever. Thus, prompt removal or an attached tick is important. The most common site of attachment varies important. The most common site of attachment varies between individual species, with between individual species, with IxodesIxodes preferring the preferring the trunk, trunk, AmblyommaAmblyomma preferring the lower extremities, and preferring the lower extremities, and DermacentorDermacentor preferring the head, neck, or upper trunk [ preferring the head, neck, or upper trunk [44]. ]. In addition to preferred attachment site, there is In addition to preferred attachment site, there is considerable variability among tick species in terms of body considerable variability among tick species in terms of body size, shape, color, and location of origin.size, shape, color, and location of origin.

Within the medical community, these ectoparasites are Within the medical community, these ectoparasites are most notorious for the transmission of a variety of most notorious for the transmission of a variety of pathogens that can cause a spectrum of clinical pathogens that can cause a spectrum of clinical presentations. In fact, ticks are second only to mosquitoes presentations. In fact, ticks are second only to mosquitoes as vectors of disease in humans, causing more than as vectors of disease in humans, causing more than 100,000 cases of illness worldwide [100,000 cases of illness worldwide [55]. Tick-borne diseases ]. Tick-borne diseases tend to be species and region specific. For example, tend to be species and region specific. For example, Ixodes Ixodes scapularisscapularis is well known for its association with Lyme is well known for its association with Lyme disease and babesiosis in the Northeastern United States, disease and babesiosis in the Northeastern United States, whereas whereas Dermacentor andersoniDermacentor andersoni is the primary vector for is the primary vector for Rocky Mountain spotted fever in the Western states. Rocky Mountain spotted fever in the Western states. Antibiotics in the tetracycline family are most often the Antibiotics in the tetracycline family are most often the treatment of choice for tick-borne diseases.treatment of choice for tick-borne diseases.

In addition to spreading tick-borne pathogens, tick In addition to spreading tick-borne pathogens, tick attachment may also cause a hypersensitivity reaction at attachment may also cause a hypersensitivity reaction at the location of the bite. These reactions have a wide variety the location of the bite. These reactions have a wide variety of presentations and may appear as nodular, papular, or of presentations and may appear as nodular, papular, or vesiculobullous lesions. The patient may present with an vesiculobullous lesions. The patient may present with an expanding erythematous plaque that may be confused with expanding erythematous plaque that may be confused with erythema migrans. However, unlike erythema migrans, erythema migrans. However, unlike erythema migrans, hypersensitivity reactions are highly pruritic, tend not to hypersensitivity reactions are highly pruritic, tend not to display central clearing, and reach a maximum diameter display central clearing, and reach a maximum diameter within two to three days [within two to three days [44].].

Histologically, tick bite reactions often display endothelial Histologically, tick bite reactions often display endothelial swelling as well as a wedge-shaped perivascular chronic swelling as well as a wedge-shaped perivascular chronic inflammation composed of eosinophils and CD30+ inflammation composed of eosinophils and CD30+ lymphocytes [lymphocytes [44]. On occasion, one may find intravascular ]. On occasion, one may find intravascular eosinophilic deposits within areas of the reaction. In these eosinophilic deposits within areas of the reaction. In these cases, it can be difficult to distinguish tick-bite cases, it can be difficult to distinguish tick-bite hypersensitivity from the histological findings in hypersensitivity from the histological findings in cryoglobulinemia [cryoglobulinemia [66]. Whereas their presence is obviously ]. Whereas their presence is obviously helpful in diagnosis, tick mouthparts (Figures 1 and 2) are a helpful in diagnosis, tick mouthparts (Figures 1 and 2) are a relatively uncommon finding on biopsy. Clinical history as relatively uncommon finding on biopsy. Clinical history as well as the extent and type of inflammatory infiltrate prove well as the extent and type of inflammatory infiltrate prove to be valuable clues when distinguishing between these two to be valuable clues when distinguishing between these two disease processes [disease processes [66]. Once the diagnosis is made, ]. Once the diagnosis is made, treatment for hypersensitivity reactions can involve topical treatment for hypersensitivity reactions can involve topical or intralesional corticosteroids.or intralesional corticosteroids.

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© 2011 Dermatology Online Journal© 2011 Dermatology Online Journal

Ortman SA, Huerter C, Reinig E, Albertson Ortman SA, Huerter C, Reinig E, Albertson D, Sarma DP.(2011). D, Sarma DP.(2011). Unknown: Biopsy of a Unknown: Biopsy of a persistent pruritic papule on the back of a persistent pruritic papule on the back of a 75-year-old man. Dermatology Online J 75-year-old man. Dermatology Online J 17(3):11 [Pubmed-indexed in MEDLINE].17(3):11 [Pubmed-indexed in MEDLINE].