A 4-year-old boy is brought to the emergency department due to fire ant bites. The patient's mother states he was wearing flip flops and playing in the park yesterday evening when he started screaming because his feet were covered with fire ants. She brushed them off immediately, washed his feet, and applied some ice. She is concerned today because the patient has approximately 10 bites on each foot, and his feet are red, swollen, and painful. Temperature is 36.7 C (98.1 F), blood pressure is 110/60 mm Hg, pulse is 108/min, and respirations are 20/min. The patient is awake and alert. He has a normal oropharyngeal examination. Lungs are clear to auscultation bilaterally. There are approximately 10 small pustules on each foot that are surrounded by a large area of erythema and swelling contiguous to the pustules. The patient can bear weight but cries when he is asked to walk. Perfusion and sensation are normal. Which of the following is the best next step in management of this patient?

Question

A 4-year-old boy is brought to the emergency department due to fire ant bites.  The patient's mother states he was wearing flip flops and playing in the park yesterday evening when he started screaming because his feet were covered with fire ants.  She brushed them off immediately, washed his feet, and applied some ice.  She is concerned today because the patient has approximately 10 bites on each foot, and his feet are red, swollen, and painful.  Temperature is 36.7 C (98.1 F), blood pressure is 110/60 mm Hg, pulse is 108/min, and respirations are 20/min.  The patient is awake and alert.  He has a normal oropharyngeal examination.  Lungs are clear to auscultation bilaterally.  There are approximately 10 small pustules on each foot that are surrounded by a large area of erythema and swelling contiguous to the pustules.  The patient can bear weight but cries when he is asked to walk.  Perfusion and sensation are normal.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d1d6_934e_bc81_494e01b28813_MD0003_00 This patient has developed a local allergic response (swelling and erythema contiguous to the site of the sting) to multiple stings from imported fire ant (IFA) bites. Local and systemic reactions can occur in response to a sting. Wheal-and-flare reactions occur within a few minutes of the encounter and are accompanied by a burning, stinging pain. Sterile pustules develop within 24 hours due to venom alkaloids. They should be left intact and will resolve within a week. These minor reactions do not require treatment. Large local reactions (LLRs), as seen in this patient, are an exaggerated, local IgE-mediated response to proteins in the venom of IFAs, characterized by erythema, warmth, and swelling. LLRs develop within the first 24 hours (as in this case) and extend to ~10 cm or more contiguously from the site of the sting. Swelling can be significant enough to cause vascular compromise (absent in this patient with normal perfusion and sensation), but this is rare. The lesions contain fibrin, eosinophils, neutrophils, and lymphocytes. They are treated with topical high-potency corticosteroids (eg, clobetasol 0.05% ointment) and oral antihistamines. In patients with severe local symptoms, a short course of oral prednisone can be prescribed. Systemic reactions (eg, vomiting, urticaria, swelling of the airway, bronchospasm, shock, hypotension) can also occur and should be treated similarly to anaphylaxis with intramuscular or intravenous epinephrine. This patient's localized swelling in the feet with no systemic manifestations of anaphylaxis (eg, normal vital signs, clear lungs, normal oropharyngeal examination) makes a systemic reaction unlikely (Choice A). (Choice C) Oral clindamycin is used to treat cellulitis. The skin findings of cellulitis and LLRs (eg, erythema, warmth, tenderness) overlap; however, superinfections are uncommon in insect bites and would generally occur 3-5 days after the initial bite, not within the first 24 hours, as in this patient. Other infectious symptoms (eg, fever) would more likely be present in cellulitis. (Choice D) Unroofing the sterile pustules caused by stings from IFAs can lead to a secondary infection. Topical antimicrobial cream is not indicated unless an infection is present (unlikely in <24 hr, as in this case). Infections are uncommon in part because IFA venom contains antimicrobial properties. Educational objective: Bites from imported fire ants cause sterile pustules that should be left intact to prevent secondary infections. Pustules and small local reactions require no treatment. Large local reactions can be treated successfully with antihistamines and topical steroids. References: Large local reactions and systemic reactions to insect stings: similarities and differences. (http://www.ncbi.nlm.nih.gov/pubmed/32298380)

A 4-Year-Old Boy Is Brought to the Emergency Department Due