Tinea infections are specific fungal infections caused by dermatophytes that obtain their nutrition exclusively from keratin (e.g. stratum corneum, hair, nails).  The most common tinea infections are caused by dermatophytes (epidermophyton, trichophyton, or microsporum) or by non-dermatophyte molds or yeast (e.g. G candida).[i]

Clinical presentation

          Clinical signs of fungal infections affecting the skin are scaliness, erythematous plaques, and annular plaques.  A definitive fungal odor may sometimes be present.  Rarely are the lesions vesicular or pustular, although some rare types may cause pustules.  The specific disorder is named according to the body part infected as follows: Tinea capitis (scalp), Tinea barbae (beard), Tinea corporis (body), Tinea cruris (genital area), Tinea pedis (feet) and tinea unguium or onychomycosis (nail). 

Onychomycosis is characterized by thick, yellow nails due to hyperkeratosis of the under-surface of the nail, yellow or chalky-white discoloration, longitudinal folds in the nail bed, accumulation of debris under the nail causing the nail to separate from the nail bed, crumbling distortion of the nail, and possible loss of the nail.[ii] In addition, there may be surrounding scaly skin.  This condition is most frequently observed on the toes of patients with diabetes or with peripheral vascular disease.

Tinea corporis (also known as ringworm) may occur under compression bandages if the skin tends to be moist, and candidiasis, a yeast-like fungus of the skin, can affect the mucous membranes, the gastrointestinal tract, and the vagina/perineal region (frequently seen on the skin of patients with urinary incontinency).

Tinea pedis most frequently occurs on the soles and toe spaces of the feet and is characterized by intertriginous dermatitis with maceration, peeling, and fissuring the toe interspaces.  If caused by Trichophyton mentagrophytes, the acute inflammatory phase may present with pustules, vesicles, and sometimes bullae.[iii]

Differential diagnosis

          Histological features of tinea infections include neutrophils in the stratum corneum, often with parakeratosis and a variable inflammatory response in the dermis.  The organisms are best visualized by histological biopsy with periodic acid-Schiff (PAS) staining or polymerase chain reaction (PCR), and a potassium hydroxide (KOH) prep may show branching septate hyphae.[iv] 

Medical Management

Systemic treatment with antifungal agents is used for severe cases only.  A systematic review by Gupta, et al. concluded the following guidelines for the treatment of onychomycosis:  first-line therapy is selected based on nail plate involvement with terbinafine for severe cases (>60% involvement), terbinafine or efinaconazole for moderate cases (20-60% involvement), and efinaconazole for mild cases (<20% involvement).  Comorbidities, patient preference and adherence, or nail thickness may result in the use of alternative oral or topical antifungals.[v]  A Cochrane review by Kreijkamp-Kaspers, et al, concluded that “terbinafine probably leads to better cure rates than azoles with the same risk of adverse events.”[vi]

Wound Management

The mainstay of treatment for fungal infections is topical antifungal creams, e.g. imidazoles, triazoles, and allylamines.  The drugs recommended for tinea cruris and tinea corporis are terbinafine and naftifine, both with infrequently reported side effects.[vii]  Two topical drugs recommended for onychomycosis are efinaconazole and tavaborole.[viii] They are applied twice daily and need to be used for at least a week after symptoms have resolved.  Topical treatment of onychomycosis may take several months before visible changes in the nail can be observed, and recurrence is frequent. 

Urea, in concentrations over ≈30%, is a dermatolytic agent that softens and hydrates the nail plate by denaturing the nail keratin, and thus may enhance the drug penetration and promote avulsion of the affected nail, thereby improving treatment efficacy.¹ 

Laser systems are a non-pharmaceutical treatment for onychomycosis which work by inhibiting the growth of the fungus by selective photothermolysis.  The cumulative cure rate of laser treatment has been shown to be higher when CO₂ lasers are used.  Potential adverse effects include pain and bleeding.[ix]^,[x]

In summary, tinea or fungal infections can affect any part of the body and are difficult to cure, especially for onychomycosis which occurs on the nails of patients with diabetes or peripheral arterial disease.  Oral medication may have side effects that need to be closely monitored, and topical applications need to be used after signs are no longer visible in order to prevent recurrence.

[i] Dars S, Banwell HA, Matricciani L.  The use of urea for the treatment of onychomycosis: A systematic review.  J Foot Ankle Res.  2019;12:22.  Doi: 10.1186/s13047-019-0332-3.  Accessed 1/26/20.

[ii] Hamm R, Shah JB.  Atypical wounds.  In Hamm R (Ed). Text and Atlas of Wound Diagnosis and Treatment, 2^nd edition.  New York: McGraw-Hill Education.  2019;235-268.

[iii] Thapa RK, Choi JY, Han SD, Lee GH, Yong CS, et al. Therapeutic effects of a novel DA5505 formulation on a guinea pig model of tinea pedis.  Dermatologica Sinica. 2017;35:59-65).

[iv] Falanga V, Phillips T, Harding K, Moy R, Peerson L. London, UK:Martin Dunitz. 2000;61-97,189-227.

[v] Gupta AK, Sibbald RG, Andriessen A, Belley R, Boroditsky A, et al. Toenail onychomycosis – A Canadian approach with a new transungual treatment: Development of a clinical pathway. J Cutan Med Surg. 2015;19(5):440-449.

[vi] Kreijkamp-Kaspers S, Hawke K, Guo L, Kerin G, et al. Oral antifungal medication for toenail onychomycosis. Cochrane Database Syst Rev. 2017;July 14:7:CD010031.

[vii] El-Gohary M, van Zuuren EJ, Fedorowicz Z, Burgess H, et al.  Topical antifungal treatments for tinea cruris and tinea corporis.  Cochrane Database Syst Rev. 2014;2014 Aug 4;(8):CD009992.

[viii] Thomas J, Peterson GM, Christenson JK, Kosari S, Baby KE. Antifungal drug use for onychomycosis.  Am J Ther.  2019;26(3):e388-e396.

[ix] Yeung K, Ortner VK, Martinussen T, Paasch U, Haedersdal M.  Efficacy of laser treatment for onychomycotic nails: A systematic review and meta-analysis of prospective clinical trials. Lasers Med Sci. 2019;34(8):1513-1525.

[x] Ma W, Si C, Kasyanju Carrero LM, Liu HF, et al. Laser treatment for onychomycosis: A systematic review and meta-analysis. Medicine (Baltimore). 2019 Nov,98(48):e17948.