Clinical Challenge: Blisters on Instep - MPR

Clinical Challenge: Blisters on Instep

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A 56-year-old man presents with a complaint of itchy blisters on his feet. The condition has been present for several months and increases in severity during warmer weather. The patient is in good health and takes no medications. He is currently employed as a lineman for a telephone company and spends much of his time outdoors. Examination of his feet reveals well-demarcated zones of scaling involving the plantar and medial surfaces accompanied by scattered vesicles. Several nails exhibit subungual hyperkeratosis.

Inflammatory or vesicular tinea pedis is 1 of the 4 subtypes of tinea pedis, a common fungal infection that affects approximately 70% of the population at some point in their life.1 Unlike interdigital and moccasin type tinea pedis, which are predominately...

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Inflammatory or vesicular tinea pedis is 1 of the 4 subtypes of tinea pedis, a common fungal infection that affects approximately 70% of the population at some point in their life.1 Unlike interdigital and moccasin type tinea pedis, which are predominately caused by Trichophyton rubrum, vesicular and ulcerative type tinea pedis are caused by T. interdigitale.1

Vesicular tinea pedis typically presents as small pruritic vesicles and/or pustules accompanied by scale. The vesicles tend to appear on nonweight-bearing surfaces of the feet such as the arch and medial aspect of the foot.1

In the initial stages of the infection, the skin appears to be dry and scaly with vesicles subsequently arising on erythematous bases. The vesicles may be itchy or painful and are the result of an acute inflammatory response. Pustules may appear due to the accumulation of polymorphonuclear cells. Risk factors for tinea pedis include heat, humidity, use of occlusive shoes, and exposure to swimming pools.2

Although diagnosis of tinea pedis is usually made clinically, microscopic examination of skin scrapings or fungal culture can aid in the diagnosis of difficult cases.3 The condition is most commonly treated with topical antifungal agents. Many antifungal formulations are available either by prescription or over the counter and the majority have equal efficacy, safety and tolerability.4

Sara Mahmood, DPN, is a podiatry/dermatology fellow at the DermDox Centers for DermatologyStephen Schleicher, MD, is director of the DermDox Center for Dermatology in Pennsylvania, as well as associate professor of medicine at Commonwealth Medical College and clinical instructor of dermatology at Arcadia University and Kings College.  

References

1. Ilkit M, Durdu M. Tinea pedis: the etiology and global epidemiology of a common fungal infectionCrit Rev Microbiol. 2015;41(3):374-388. doi: 10.3109/1040841X.2013.856853

2. Gentles JC, Evans EG. Foot infections in swimming baths. Br Med J. 1973;3(5874):260-262. doi: 10.1136/bmj.3.5874.260

3. Ely JW, Rosenfeld S, Seabury Stone M. Diagnosis and management of tinea infectionsAm Fam Physician. 2014;90(10):702-710.

4. Rotta I, Sanchez A, Gonçalves PR, Otuki MF, Correr CJ. Efficacy and safety of topical antifungals in the treatment of dermatomycosis: a systematic reviewBr J Dermatol. 2012;166(5):927-933. doi: 10.1111/j.1365-2133.2012.10815.x