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A 52-year-old woman presents with a history of a tick bite that occurred approximately 8 months ago. The patient notes she found a tick attached to her right inner thigh. The tick was sent to a laboratory and tested positive for anaplasmosis. She was then placed on a 10-day course of doxycycline. An itchy pimple has developed at the site of the original bite. It is surrounded by a reddened area that has gradually turned dark. On several occasions, the patient has attempted to “pick off” the raised area to no avail. Examination reveals a dusky red, firm papule surrounded by hyperpigmentation.
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Tick bites may induce an immediate papular response as well as a late foreign body-type reaction.1 Tick bite granuloma is a fibrous nodule that develops at the site where a tick was previously attached.2 The lesion may be erythematous with edema and central crust or necrosis.3 The area is typically pruritic and can persist for months to years.
Retention of tick mouthparts and saliva is believed to be responsible for inducing a chronic immune reaction. Histopathologic examination may reveal a granulomatous reaction as well as tick remnants.4
Tick bite granuloma may spontaneously resolve. For patients who prefer treatment, options include topical corticosteroids and intralesional corticosteroid injections. To dampen the underlying immune response, full excision to completely remove embedded tick parts and remnants of saliva may be the treatment of choice.2
Brittany Spinosa-Weber, PA-C, works at the DermDox Dermatology Centers in Bethlehem and Leola, Pennsylvania. Stephen Schleicher, MD, is director of the DermDox Dermatology Centers, associate professor of medicine at Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.
References
1. Haddad V Jr, Haddad MR, Santos M, Cardoso JLC. Skin manifestations of tick bites in humans. An Bras Dermatol. 2018;93(2):251-255. doi:10.1590/abd1806-4841.20186378
2. Hirota K, Kurosawa Y, Goto K, Adachi K, Yoshida Y, Yamamoto O. Tick bite granuloma: recommendations for surgical treatment. Yonago Acta Med. 2015;58(1):51-52.
3. Ackerman AB, Metze D, Kutnzer H. Erythematous papules and nodules after tick bite. Am J Dermatopathol. 2002;24(5):427-428. doi:10.1097/00000372-200210000-00010
4. Castelli E, Caputo V, Morello V, Tomasino RM. Local reactions to tick bites. Am J Dermatopathol. 2008;30(3):241-248. doi:10.1097/DAD.0b013e3181676b60
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