By Adi Pajazetovic, DPM, Kalani Parker, DPM

Tinea pedis resistant to treatment may require systemic antifungals

History

A 67-year-old male with no known significant past medical history presented to clinic with an itchy dermatitis like lesion within his left fourth web space. Lesion has been present for an undefined length of time.

Physical Examination

Patient presented with an eczematous/tinea like lesion within the left fourth web space along with maceration to the area.

Diagnostic Testing

A shave biopsy was performed and a submission of a skin fragment measuring 0.3 x 0.3 x 0.1 cm was received to confirm diagnosis of tinea.

Histological Findings

The received specimen was sectioned, and the sections demonstrated scattered neutrophils within the stratum corneum. A periodic Acid Schiff (PAS) stain test was performed, which highlighted septated fungal hyphae, morphologically consistent with dermatophytes within the keratin layer. A PAS is commonly used stain in mycoses diagnosis as it highlights the carbohydrate rich cell wall of fungi¹.

Discussion

Tinea pedis is one of the most common fungal pedal skin infections and is caused by a dermatophyte. It can present as an interdigital manifestation, moccasin patterned, or with inflammatory vesicles, and can often be associated with onychomycosis². The condition generally affects an older population and can be as prevalent as 70% of the population .

The dermatophytes are filamentous fungi in the genera Trichophyton, Microsporum and Epidermophyton. They metabolize and subsist on keratin and infection typically is superficial involving the epidermis. The clinical features include interdigital, hyperkeratotic and vesiculobullous tinea pedis. The interdigital tinea pedis manifests as pruritic, erythematous erosions or scales between the toes, especially in the third and fourth digital interspaces³.  BakoDx now offers a web space DNA test that can help differentiate the cause of the interdigital infections. Infectious agents tested include fungi such as dermatophytes and specific bacterial agents as well. The sampling is a simple shave biopsy of the interdigital lesion. All that is needed is a visible sample of tissue. This easy procedure will aid in the treatment of the infection as it specifies the inciting organism.

Treatment

Tinea pedis rarely causes significant morbidity or mortality, but there is some evidence that it can act as a portal of entry for bacteria causing bacterial cellulitis. Topical antifungal treatment is generally adequate. For extensive infections and especially involving immunocompromised patients, oral therapy may be required. Relapse from inadequate therapy is common and reinfection can reoccur in 10% of cases. Tinea pedis resistant to treatment may require systemic antifungals such as terbinafine, fluconazole, or itraconazole. In cases involving both fungal and bacterial infections, a concomitant antibiotic therapy is justified.

Most superficial cutaneous dermatophyte infections are managed with topical therapy such as azoles, Nystatin, etc. Oral treatment with terbinafine, itraconazole, fluconazole, and griseofulvin is used for recalcitrant infections. The use of combination antifungal and corticosteroids is discouraged as it is unnecessary to achieve cure and increases the risk of steroid induced skin atrophy³.

References:

1: Wang, Michael Z (02/01/2017). “Correlation between histopathologic features and likelihood of identifying superficial dermatophytosis with periodic acid Schiff-diastase staining: a cohort study”. Journal of cutaneous pathology (0303-6987), 44 (2),   152.

2: Usatine, R. P., Smith, M. A., Mayeaux, E. J., & Chumley, H. S. (2019). The color atlas and synopsis of family medicine. New York: McGraw-Hill Education.

3: Goldstein AO, Goldstein BG. Dermatophyte (tinea) infections. UpToDate, 2019.

By Courtney McClurkin, DPM; Andrew Olson, DPM

Molluscum contagiosum can be confused with a variety of different skin pathologies

History

A 25 year old male with no known significant past medical history presents with a pigmented lesion to plantar aspect of his left foot present for an undetermined period of time.

Physical Examination

A raised red and black 3mm lesion is seen on the plantar aspect of left foot.

Diagnostic Testing

A 2mm punch biopsy was performed with clinical concern to rule out melanoma.

Histological Findings

Typical histological features of molluscum contagiosum were identified including molluscum bodies, which are intracytoplasmic eosinophilic structures contained within epidermal cells.  These molluscum bodies become basophilic in the upper part of the epidermis, and are found in high numbers in the horny layer.  There is also a dense polymorphonuclear infiltrate noted adjacent to the epithelium containing the molluscum bodies.

Diagnosis

Molluscum contagiosum

Discussion

Molluscum contagiosum is a skin infection that is caused by a poxvirus.  Transmission of the molluscum contagiosum virus is through contact with an infected person or contaminated surface.  It is most commonly found in young children, but is also notorious for sexual transmission among adults and adolescents.  Transmission rates are generally similar for the immunocompromised.  However, the lesions can be more numerous, appear in atypical locations, and be more resistant to treatment.  The virus incubates for a period of 14 days to 6 months, followed by formation of slowly enlarging, single or multiple lesions.  The lesions most commonly appear as pearly, umbilicated papules.  They can become inflamed and erythematous, causing a “molluscum dermatitis”.  Most cases are self-limiting, though crops of lesions may come and go over the span of months.  There are, however, a plethora of treatment options ranging from physical destruction to systemic treatments.

Clinically, molluscum contagiosum can be confused with a variety of different skin pathologies, including but not limited to: verruca vulgaris, condyloma, nevocellular nevus, basal cell carcinoma, keratoacanthoma, lichen planus, eczema, foreign body granuloma, sarcoidosis, folliculitis, and true epidermal cyst.

Two histologic variants exist.  The pseudocystic variant is distinguished by invagination of colonized epithelium of dilated horn-filled infundibula bordered by a thick epidermis and are filled with compact, thick keratin.  In the polyploid variant, the dermis located beneath molluscum contagiosum has loose collagen fibers, dilated vessels, and inflammatory infiltrate.  Molluscum bodies are the most distinguishing  histologic feature.  These are large cells with cytoplasmic eosinophilic inclusions that contain viral particles.

Associated lesions with molluscum contagiosum are common, including true epidermal cysts, nevocellular nevus, Unna nevus, Clark nevus, soft fibromas, and Kaposi sarcoma.  Abscesses can be associated due to discharge of molluscum bodies to the dermis, followed by release of proinflammatory cytokines and activation of complement pathway.

Treatment

While molluscum contagiosum is typically self-limiting within 6 months, there are treatment options available.  Treatment is initiated in order to alleviate discomfort produced by itchy or painful lesions, for cosmetic reasons, to prevent spread of lesions, as well as to prevent trauma, scarring, and secondary infection of lesions.

Surgical treatments include: cryotherapy, curettage, punch biopsy, manual excision, electric cauterization, and laser therapy.

Topical treatments include: acidified nitrite, adapalene, Australian lemon myrtle oil, benzoyl peroxide, bromogeramine, cantharidin, cidofovir, diphencyprone, griseofulvin, honey, hydrogen peroxide, imiquimod, iodine, phenol, podophylotoxin (HIV patients), potassium hydroxide, salicylic acid, tea tree oil, and tretinoin.

Systemic treatments include cimetidine, griseofulvin, and cidofovir (in HIV-infected patients).

References:

Cribier, B., Y. Scrivener, and E. Grosshans. Molluscum contagiosum: histologic patterns and associated lesions. The American Journal of Dermatopathology 23(2): 99-103 (2001).

Mancini, A.J. and A. Shani-Adir. Other Viral Diseases. Dermatology 3^rd ed. (2012): p. 1358-59.

Van der Wouden, J.C., et. al. Interventions for cutaneous molluscum contagiosum (review). Cochrane Database of Systematic Reviews Issue 5, Art. No.: CD004767 (2017).