A 45-year-old obese woman with diet-controlled diabetes mellitus comes to the physician with mild pruritus in both axillary areas. Physical examination findings are shown in the image below.

Examination with Wood's lamp shows red fluorescence in the affected areas. Which of the following is the most likely diagnosis?

Question

A 45-year-old obese woman with diet-controlled diabetes mellitus comes to the physician with mild pruritus in both axillary areas.  Physical examination findings are shown in the image below.

Examination with Wood's lamp shows red fluorescence in the affected areas.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Erythrasma presents with well-demarcated, pruritic, red-brown plaques, most commonly in interdigital (especially the toes) and intertriginous areas. It can occasionally have a fine "cigarette paper" scale. It is a superficial skin infection caused by Corynebacterium minutissimum and can be seen in healthy patients, although those with impaired immune systems (eg, diabetes) are at increased risk. C minutissimum, which is part of normal skin flora, can overgrow and cause disease under conditions of moisture and occlusion. The diagnosis of erythrasma is based on its appearance on examination, but can be confirmed by examining the affected areas under a Wood's lamp and observing its classic coral-red appearance. The red color is due to the production of porphyrins by the bacteria, though they may be washed away by bathing producing a false-negative result. Limited disease is treated with topical antibiotics (clindamycin 1%). Topical antifungals (miconazole) can also be used for limited disease as they can be effective for erythrasma and coexisting dermatophyte infection. Systemic therapy with oral macrolides (erythromycin or clarithromycin) is reserved for more extensive disease (multisite disease). (Choice A) Candidal intertrigo is a common pruritic, intertriginous infection. It has risk factors similar to erythrasma, and also occurs in areas of moist, occluded skin. Typical lesions are erythematous, macerated plaques with peripheral scaling. Candidal intertrigo is diagnosed by examining skin scrapings in potassium hydroxide (KOH) showing budding yeast with septate hyphae. It does not have a red appearance under a Wood's lamp. Candidal intertrigo (Choice C) The plaques of inverse psoriasis are present in intertriginous areas such as the axillae and inframammary areas, as opposed to typical plaque psoriasis which appears on the extensor surfaces of extremities, scalp, and back. The plaques are also erythematous and well-demarcated but may not have the typical psoriatic scale and are frequently not pruritic. The lesions do not exhibit any fluorescence under Wood's lamp examination. inverse psoriasis (Choice D) Microsporum is one of the 3 most common causative agents of tinea infections. Tinea infections also affect otherwise healthy individuals, but patients with some level of immunosuppression are at increased risk. The typical lesion is an erythematous, ring-shaped, well-demarcated plaque and can be associated with pruritus. Diagnosis is made by demonstrating septate hyphae on potassium hydroxide (KOH) skin scrapings. One form of tinea capitis can give silver-blue fluorescence on Wood's lamp examination, but none are associated with the red glow of erythrasma. tinea infections (Choice E) Seborrheic dermatitis is a chronic, recurring, and usually very mild form of dermatitis that has an unknown etiology (although Malassezia has been indirectly implicated). More severe disease presents with erythematous plaques with yellow scale and occasional pruritus. Seborrheic dermatitis is most commonly seen on the scalp, face, trunk, and intertriginous areas and is diagnosed clinically. It has no characteristic finding under a Wood's lamp. Seborrheic dermatitis Educational objective: Erythrasma is a superficial skin infection caused by Corynebacterium minutissimum. The lesions are well-demarcated, red-brown, pruritic, and most common in moist interdigital or intertriginous areas. Diagnosis is clinical and can be confirmed by the lesions' red fluorescence under a Wood's lamp. Limited infection is treated with topical antibiotics, while multisite disease may require oral macrolides. __________ References: Images in clinical medicine. A brilliant case of erythrasma. (http://www.ncbi.nlm.nih.gov/pubmed/15483285)

A 45-Year-Old Obese Woman with Diet-Controlled Diabetes Mellitus Comes to the Physician