DermDx: Disfigured Fingernails

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A 45-year-old man presents to the dermatology clinic requesting treatment for disfigured fingernails. The condition began on his toenails approximately 5 years ago and then appeared on 1 fingernail 2 years later. It has since spread to 2 more fingernails. The patient denies pain and has no history of arthritis or other skin diseases. He is on no medications. Physical examination reveals dystrophic nails with subungual debris; light scaling is noted on his left sole.

Onychomycosis is a fungal infection of the nails. It is most commonly caused by the dermatophytes Trichophyton rubrum and T interdigitale; certain yeasts and molds can also cause this condition.1 Toenails are affected approximately 7 to 10 times more frequently...

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Onychomycosis is a fungal infection of the nails. It is most commonly caused by the dermatophytes Trichophyton rubrum and T interdigitale; certain yeasts and molds can also cause this condition.1 Toenails are affected approximately 7 to 10 times more frequently than fingernails.2 Concomitant tinea pedis is often noted when multiple toenails are involved.

Onychomycosis has key features that aid in the clinical diagnosis. These include longitudinal splitting of the nail plate; significant subungual debris and hyperkeratosis; thickening of the nail plate; and yellow, brown, or white nail discoloration. Based on the pattern of invasion of the nail, multiple clinical subtypes have been described, with distal lateral subungual onychomycosis being the most common subtype.2

Confirmatory testing for onychomycosis includes culture, microscopic examination of subungual hyperkeratosis with potassium hydroxide (KOH), or histopathology of nail clippings stained with periodic acid-Schiff (PAS) or Gömöri methenamine silver (GMS).3 For KOH or fungal culture, the most proximal portion of the subungual debris is best collected for sampling.

Treatment of onychomycosis can be challenging as fingers and toenails take months to grow out. Terbinafine is the most common oral medication for first-line treatment.4 Topical treatment options include ciclopirox, efinaconazole, and tavaborole. Topical medications may also be used as maintenance therapy. In pediatric patients, efinaconazole has been recommended as the first-line option followed by terbinafine if oral treatment is needed.4 In severe cases, complete resolution might not be possible.5

Laser therapy has become increasingly popular for cosmetic results but clinical efficacy is variable.6 Patient education, including discussion of personal hygiene, footwear, and sock sanitation is important to help minimize recurrence.6

Sara Mahmood, DPM, is a podiatrist who completed a joint dermatology/podiatry fellowship and is on staff at DermDox Dermatology Centers. Stephen Schleicher, MD, is director of the DermDox Dermatology Centers, associate professor of medicine at Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.

References

1. Gupta AK, Mays RR, Versteeg SG, Shear NH, Piguet V. Update on current approaches to diagnosis and treatment of onychomycosis. Expert Rev Anti Infect Ther. 2018;16(12):929-938. doi:10.1080/14787210.2018.1544891

2. Leung AKC, Lam JM, Leong KF, et al. Onychomycosis: an updated review. Recent Pat Inflamm Allergy Drug Discov. 2020;14(1):32-45. doi:10.2174/1872213X13666191026090713

3. Scher RK, Tosti A, Joseph WS, et al. Onychomycosis diagnosis and management: perspectives from a joint dermatology-podiatry roundtable. J Drugs Dermatol. 2015;14(9):1016-1021.

4. Lipner SR, Joseph WS, Vlahovic TC, et al. Therapeutic recommendations for the treatment of toenail onychomycosis in the US. J Drugs Dermatol. 2021;20(10):1076-1084.

5. Lipner SR, Scher RK. Onychomycosis: Clinical overview and diagnosis. J Am Acad Dermatol. 2019;80(4):835-851. doi:10.1016/j.jaad.2018.03.062

6. Gupta AK, Versteeg SG. A critical review of improvement rates for laser therapy used to treat toenail onychomycosis. J Eur Acad Dermatol Venereol. 2017;31(7):1111-1118. doi:10.1111/jdv.14212

7. Daggett C, Brodell RT, Daniel CR, Jackson J. Onychomycosis in athletes. Am J Clin Dermatol. 2019;20(5):691-698. doi:10.1007/s40257-019-00448-4

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