Identifying Signs of Tinea Pedis: A Key to Understanding Clinical Variables

October 2015 | Volume 14 | Issue 10 | Supplement Individual Articles | 42 | Copyright © October 2015

Theresa N. Canavan MD and Boni E. Elewski MD

Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL

table 5
pedis and a single hand with tinea manuum; or alternatively with 1 foot and 2 hands affected (Figure 3). Prolonged moccasin type of tinea pedis is a major risk factor for developing onychomycosis.
A less common presentation of tinea pedis is the vesicular type of tinea pedis where patients develop small vesicles on a background of erythema localized to the instep or medial plantar surface of their feet. These lesions are painful and pruritic, and develop far more rapidly than the other varieties of tinea pedis. Vesicular type of tinea pedis is the only subtype of tinea pedis that is exclusively associated with infection from organisms from the T. mentagrophytes complex infection, typically the zoophilic species.14
The acute ulcerative type is very rare and typically results from an exacerbation of the more common interdigital tinea pedis. Patients with acute ulcerative tinea pedis will present with ulcers and erosions in the web spaces between their toes, and these patients are at risk for secondary bacterial infection, which can be severe and debilitating. Patients may progress to develop cellulitis, lymphangitis, and fevers. The zoophilic variety of T. interdigitale is also implicated in this type of tinea pedis.14 Patients presenting with this type of tinea pedis are more likely to have concurrent diabetes, immunosuppresion, or peripheral vascular disease.
In addition to the above mentioned clinical patters of infection, a noteworthy proportion of people are carriers of the dermatophytes implicated in tinea pedis. In epidemiological studies, up to 14% of patients may have occult tinea pedis as defined by “normal” appearing feet, no symptoms concerning for tinea pedis, and a positive mycologic culture from scrapings of feet.20 Clinical findings of tinea pedis can be subtle, especially for moccasin type tinea pedis, which may have only a fine collarette of scale. Although not a distinct subtype of tinea pedis, it is still important for the clinician to be aware of the concept of occult tinea pedis because it is quite common. Patients with occult infection may be considered to have an early stage of tinea pedis and are at risk of transmitting the infection to other people.20 In one study, the overwhelming majority of patients with occult tinea pedis had onychomycosis; thus, patients with onychomycosis without clinical signs of tinea pedis ought to be evaluated for occult tinea pedis.20
A variety of clinical exam findings should alert the clinician to the fact that a patient may have tinea pedis (Table 4). Patients who have either tinea manuum or tinea cruris should be examined for possible tinea pedis, as these infections often coexist. Similarly, as mentioned above, patients who have onychomycosis of either the fingernails or toenails should be evaluated for tinea pedis. Indeed, only patients with occult or clinically present tinea pedis will develop onychomycosis, so all patients with onychomycosis should be evaluated for evidence of tinea pedis.21

Differential Diagnosis

The differential diagnosis for tinea pedis includes both infectious and non-infectious etiologies (Table 5). Intertrigo with secondary bacterial or candidal infection can masquerade
table 6