A 45-year-old man comes to the physician for evaluation of a rash on his right leg. He initially developed a minor traumatic laceration 3 weeks ago. He applied hydrogen peroxide and an over-the-counter topical antibiotic cream (neomycin-polymyxin-bacitracin). The laceration improved during the first 4 days, but then a rash with significant pruritus and clear drainage developed around the wound over the next 2 weeks. The patient has a history of diabetes, hypertension, and hypercholesterolemia. His current medications include metformin, lisinopril, and rosuvastatin. He has no history of tobacco or alcohol use.
His vital signs are within normal limits. Skin examination of the right leg is shown below. There is clear drainage from the lesions and warmth to palpation. There is no tenderness. Examination of the extremities shows no pedal or ankle edema. The remainder of his physical examination is normal.

Which of the following is the most likely diagnosis?

Question

A 45-year-old man comes to the physician for evaluation of a rash on his right leg.  He initially developed a minor traumatic laceration 3 weeks ago.  He applied hydrogen peroxide and an over-the-counter topical antibiotic cream (neomycin-polymyxin-bacitracin).  The laceration improved during the first 4 days, but then a rash with significant pruritus and clear drainage developed around the wound over the next 2 weeks.  The patient has a history of diabetes, hypertension, and hypercholesterolemia.  His current medications include metformin, lisinopril, and rosuvastatin.  He has no history of tobacco or alcohol use.
His vital signs are within normal limits.  Skin examination of the right leg is shown below.  There is clear drainage from the lesions and warmth to palpation.  There is no tenderness.  Examination of the extremities shows no pedal or ankle edema.  The remainder of his physical examination is normal.

Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

This patient's presentation is consistent with allergic contact dermatitis (ACD), most likely from topical antibiotic use. ACD is a delayed hypersensitivity response to an exogenous agent such as latex, soaps/cleaning agents, cosmetic products, or topical medications. Patients typically develop erythematous, indurated, and pruritic plaques around the contact site. Severe cases can present with edema, drainage, and vesiculation with bullae. Continued exposure to the offending agent can lead to dry, scaly skin. Diagnosis of ACD is usually made based on clinical findings, but some cases may require skin biopsy and/or patch testing for confirmation. ACD will often resolve promptly following discontinuation of the offending agent, though topical glucocorticoids may be useful for patients with significant discomfort. Patients should also be counseled that most minor cuts and scrapes do not require topical antibiotics as these would only increase ACD risk and contribute to antibiotic resistance. (Choice B) Erysipelas is a superficial skin infection involving the upper dermis and subcutaneous fat. Patients develop well-demarcated plaques with erythema, edema, and warmth. In addition, systemic symptoms (eg, fever, chills) are usually present, but significant pruritus is not seen. Erysipelas (Choice C) Necrotizing fasciitis is a deep skin infection with progressive destruction of the muscle fascia. Patients develop systemic signs (eg, fever, hypotension) with skin erythema, edema, warmth, and exquisite tenderness without significant pruritus. (Choice D) Stevens-Johnson syndrome is usually caused by systemic medications. It presents with a flu-like prodrome followed by mucocutaneous lesions. The lesions begin as erythematous macules that subsequently develop blistering, necrosis, and sloughing. Stevens-Johnson syndrome (Choice E) Toxic shock syndrome is characterized by rapid onset of severe systemic signs (eg, fever, hypotension) associated with a diffuse erythematous rash. Educational objective: Allergic contact dermatitis is frequently caused by latex, soaps/cleaning agents, cosmetic products, and topical medications. It is characterized by local erythema, pruritus, vesiculation, and swelling. __________ References: Contact dermatitis to topical medicaments: a retrospective chart review from the Ottawa Hospital Patch Test Clinic. (http://www.ncbi.nlm.nih.gov/pubmed/23010827) Allergic contact dermatitis to antibacterial agents. (http://www.ncbi.nlm.nih.gov/pubmed/19386217)

A 45-Year-Old Man Comes to the Physician for Evaluation of a Rash