A 13-year-old boy is brought to the clinic by his parents due to a change in behavior. His special education teacher reported that for the last several weeks he has frequently taken off his shoes to scratch his feet during class. The patient has a history of learning disability but is otherwise healthy. Examination shows erythema and excoriations between the toes of both feet. Microscopy of skin scrapings from the rash is shown in the exhibit.

Which of the following antimicrobial drugs is likely to be the most effective against the pathogen causing this patient's condition?

Question

A 13-year-old boy is brought to the clinic by his parents due to a change in behavior. His special education teacher reported that for the last several weeks he has frequently taken off his shoes to scratch his feet during class. The patient has a history of learning disability but is otherwise healthy. Examination shows erythema and excoriations between the toes of both feet. Microscopy of skin scrapings from the rash is shown in the exhibit.

Which of the following antimicrobial drugs is likely to be the most effective against the pathogen causing this patient's condition?

Quizplus · Accepted Answer

11ec160b_3bfd_e904_9249_790b23cd2f9e_MD0001_00 This patient has a pruritic, erythematous rash affecting the feet. Microscopy of skin scrapings shows branching hyphae, confirming the diagnosis of tinea pedis (athlete's foot). Tinea pedis is a superficial infection of the epidermis caused by dermatophytes, especially Trichophyton rubrum and similar species. The organisms are widespread and are often acquired following exposure to public places while barefoot (eg, athletic facilities, swimming pools). They can also spread from other areas (eg, groin [tinea cruris], body [tinea corporis]) on the same patient via autoinoculation. Tinea pedis most commonly occurs between the toes (interdigital pattern) but in chronic cases can cause a hyperkeratotic rash extending up the sides of the feet (moccasin pattern). Tinea pedis is treated with a variety of topical antifungals, including azoles (eg, miconazole, clotrimazole), allylamines (eg, terbinafine), and tolnaftate. However, nystatin (primarily used for Candida infections) is not effective against dermatophytes (Choice D). (Choice A) Albendazole is an antihelminthic agent used to treat cutaneous larva migrans, which presents with pruritic, red/brown serpiginous tracks in the skin. The feet are typically the initial location of infection, but symptoms would not be confined to the interdigital skin. (Choice C) Topical mupirocin is used to treat impetigo, which presents with well-defined erythematous, erosive lesions with yellow crust. (Choice E) Permethrin is used for scabies, which can affect the interdigital skin but presents with small papules, pustules, and burrows. Microscopy of skin scrapings shows mites or ova and fecal matter. Educational objective: Tinea pedis is a superficial infection of the epidermis caused by dermatophytes (eg, Trichophyton rubrum). It most often presents as a pruritic, erythematous rash between the toes that frequently extends along the sole. Microscopy of skin scrapings shows branching hyphae. Treatment options include a variety of topical antifungals (eg, clotrimazole), but not nystatin.

A 13-Year-Old Boy Is Brought to the Clinic by His