Derm Dx: Redness and Swelling of the Posterior Thigh - Clinical Advisor

Derm Dx: Redness and Swelling of the Posterior Thigh

Slideshow

  • Slide

A 31-year-old woman presents with redness and swelling of her right posterior thigh. She experienced the sudden onset of sharp pain in the affected area while pulling weeds in her garden. Over the next 2 hours the site became red and swollen. The patient denies prior episode of a similar occurrence or shortness of breath, weakness, or increased heartbeat. Her medical history is positive for nickel allergy. Examination reveals an edematous, dark red plaque surrounded by a well-demarcated zone of erythema. The site was slightly warm to touch. 

A variety of insects including bed bugs, lice, ticks, fleas, and mosquitos are known to bite human skin. These insects are nonvenomous; their bites cause localized irritation as a result of noxious agents within their saliva that is deposited under...

Submit your diagnosis to see full explanation.

A variety of insects including bed bugs, lice, ticks, fleas, and mosquitos are known to bite human skin. These insects are nonvenomous; their bites cause localized irritation as a result of noxious agents within their saliva that is deposited under the skin.1  In contrast, venomous insects such as bees, wasps, and certain species of ant introduce toxins by way of stingers. More than 90% of people are stung by venomous insects during the course of their lifetime, and up to 15% experience allergic reactions.2  Anaphylaxis is the most serious consequence that is precipitated by the venom of many members of the Hymenoptera order, including insects with stingers.3 Unlike bees whose stingers are barbed and remain in the skin following a bite, the stingers of wasps are retracted and can inflict multiple wounds.

Following the sting of a bee or wasp, the majority of patients will experience variable degrees of pain, swelling, redness, and itching. Bullae and vesicles may also arise. If the stinger can be visualized in the skin, removal by scraping of the skin surface is favored over plucking, which can result in extravasation of more venom.4 Relief can be afforded by application of a cold compress, nonsteroidal anti-inflammatory medications, antihistamines, and topical steroids. If anaphylaxis is evident, subcutaneous epinephrine should be administered without hesitation. Multiple Hymenoptera bites, although uncommon, can precipitate multiple organ failure.5

Stephen Schleicher, MD, is director of the DermDox Center for Dermatology in Pennsylvania, as well as an associate professor of medicine at Commonwealth Medical College and a clinical instructor of dermatology at Arcadia University and Kings College.                                                         

References

1. Singh S, Mann BK. Insect bite reactions. Indian J Dermatol Venereol Leprol. 2013;79(2):151-164.

2. Nittner-Marszalska M, Cichocka-Jarosz E. Insect sting allergy in adults: key messages for clinicians. Pol Arch Med Wewn. 2015;125(12):929-937.

3. Szari SM, Adams KE, Quinn JM, Stokes SC, Sacha JJ, White KM. Characteristics of venom allergy at initial evaluation: is fire ant hypersensitivity similar to flying Hymenoptera? Ann Allergy Asthma Immunol. 2019;123(6):590-594.  

4. Hon KL, Leung AKC. Bee or wasp sting. Wounds. 2017;29(9):E70-E72.

5. Schmidt JO. Clinical consequences of toxic envenomations by Hymenoptera. Toxicon. 2018;150:96-104.

Next hm-slideshow in Derm DX