An 8-year-old girl is brought to the office for evaluation of a skin rash on her upper back. The rash is not painful but is mildly pruritic. She has no prior medical conditions, takes no medications, and is up to date with vaccinations. Vital signs are within normal limits. Right scapular area skin examination is shown in the exhibit. The remainder of the examination is normal. Which of the following is the most likely cause of this patient's current condition?
This patient with a mildly pruritic, polycyclic rash with a raised, scaly border and central clearing has tinea corporis. Patches of tinea corporis are typically round or ovoid but may become confluent to form a "flower petal" shape. Skin contact, especially in warm and humid environments, is a common risk factor, and patients often have concurrent infections in other body areas. Any species of dermatophyte may cause this condition, but Trichophyton rubrum is the most frequent culprit.
Dermatophyte infections (eg, tinea corporis, tinea pedis, tinea cruris) infect keratinized matter in the stratum corneum of the superficial epidermis but do not invade the dermis or subcutaneous tissues. The diagnosis is confirmed with potassium hydroxide (KOH) preparation of skin scrapings, which show the characteristic segmented hyphae and arthrospores.
(Choice A) Candida albicans is a commensal organism that is normally present on the skin. Cutaneous candidiasis (eg, intertrigo) is an inflammatory condition involving approximated skin surfaces (eg, axillae, groin); Candida most commonly causes invasive infection in immunocompromised (eg, neutropenic) patients.
(Choice B) Sunburn presents with erythema, itching, and pain in sun-exposed areas. Sunburned skin may undergo superficial desquamation (peeling), but this patient's rounded lesions with peripheral scaling are more consistent with tinea corporis.
(Choice C) Patients with untreated streptococcal pharyngitis can develop erythema marginatum, a fleeting pink or red rash with central clearing that can appear, disappear, and reappear within hours. This is a hallmark feature of rheumatic fever and is usually accompanied by other signs such as migratory arthritis, carditis, subcutaneous nodules, and Sydenham chorea.
(Choice E) Acute Lyme disease is characterized by flu-like symptoms and erythema migrans, a slowly spreading erythematous rash with central clearing at the site of the tick bite. Disseminated disease can present with multiple lesions, but the lesions are flat or only slightly raised and the border is indistinct rather than scaly; they often develop a targetoid appearance.
Educational objective:
Tinea corporis presents with round or ovoid lesions with a raised, scaly border and central clearing. Trichophyton rubrum is the most common cause and infects keratinized matter in the stratum corneum of the superficial epidermis but does not invade the dermis or subcutaneous tissues.