Updated Perspectives on the Diagnosis and Management of Onychomycosis

Figures & data

Figure 1 Scanning electron microscopy demonstrating mature fungal biofilms that were formed in 24-well plates. White arrows depict extracellular matrix covering and connecting the hyphae. (A) Trichophyton rubrum ATCC 28189. (B) Trichophyton mentagrophytes ATCC 11481. Reprinted from J Am Acad Dermatol, 1;80(4), Lipner SR, Scher RK, Onychomycosis: Clinical overview and diagnosis, 835–851, Copyright (2019), with permission from Elsevier.⁴

Figure 2 Patient with laboratory confirmed onychomycosis. (A) Clinical appearance of toenails with onycholysis, nail plate thickening and subungual debris. (B) Dermoscopy showing ruin-like appearance and streaks of various colors.

Table 1 Summary of the Diagnostic Testing Methods

Technique	Procedure	Advantages	Disadvantages	Sensitivity, % (Range)^Citation221,Citation222	Specificity, % (Range)^Citation221,Citation222	Turn Around Time	Fungal Viability	Fungal Identity
KOH and microscopy	- Clean and clip the nail - Scrape the subungual debris onto a glass slide with a #1 curette - Add KOH to dissolve larger keratinocytes - Examine using light microscopy	- Performed quickly in the office - Inexpensive	- Low sensitivity - Dependent on physician expertise - Fat droplets, air bubbles, and cotton fibers can interfere with the test	61 (44–100)	95 (75–100)	Minutes to hours (depending on nail thickness)	No	No
Fungal culture	- Clean and clip the nail - Scrape the subungual debris with a #1 curette onto a paper or cardboard with contrasting background - Grow in laboratory in sabouraud dextrose agar with or without cycloheximide	High accuracy	- High rate of false negatives - Delay in test results - Contaminants	56 (29–82)	99 (83–100)	3–4 weeks	Yes	Yes
Histopathology	- Nail is clipped and placed in 10% buffered formalin - Sample sent to laboratory for hematoxylin and eosin staining (to visualize fungal elements) and periodic acid-Schiff or Grocott methenamine-silver staining (to enhance visualization of the hyphae)	- Most sensitive technique - Can differentiate from other nail conditions	Dependent on dermatopathologist expertise	84 (61–93)	89 (44–100)	Days	No	No
PCR	-Clean and clip the nail -Scrape the subungual debris with a #1 curette onto a paper or cardboard with contrasting background -Send to specialized laboratory, where primers are used to amplify gene fragments	- Low rate of false negatives	- Expensive - Contaminants	85–100	94–100	Hours to days	No (Yes, for real-time PCR)	Yes

Abbreviations: KOH, potassium hydroxide; PCR, polymerase chain reaction.

Figure 3 A nail clipper is used to clip the most proximal area of onycholysis.

Table 2 Summary of Commonly Used Oral Onychomycosis Medications

Medication	Dosing, Fingernails	Dosing, Toenails	Mycologic Cure Rate (%), Fingernails	Mycologic Cure Rate (%), Toenails	Complete Cure Rate (%), Fingernails	Complete cure Rate (%), Toenails	US FDA Approval
Terbinafine	250 mg daily for 6 weeks	250 mg daily for 12 weeks	79	70	59	38	Yes
Itraconazole	200 mg twice daily for 1 week separated by 3 weeks of washout for 2 treatment pulses	200 mg daily for 12 weeks	61	54	47	14	Yes
Fluconazole	150 mg weekly for 6–9 months	150 mg weekly for 12–18 months	NR	47–62	NR	37–48	No

Abbreviations: FDA, Food and Drug Administration; NR, not reported; US, United States.

Table 3 Summary of FDA-Approved Topical Onychomycosis Medications

Medication	Dosing	Mycologic Cure Rate (%), Toenails	Complete Cure Rate (%), Toenails	Penetrates Nail Polish	Degrades Nail Polish	Debridement Recommended With Use	US FDA Approval
Ciclopirox lacquer	8% once daily for 48 weeks	29–36	5.5–8.5	NR	NR	Yes	Yes
Efinaconazole solution	10% once daily for 48 weeks	53.4–55.2	15.2–17.8	Yes	Yes	No	Yes
Tavaborole solution	5% once daily for 48 weeks	31.1–35.9	6.5–9.1	Yes	No	No	Yes

Abbreviations: FDA, Food and Drug Administration; NR, not reported; US, United States.

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

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Velasquez-Agudelo V, Cardona-Arias JA. Meta-analysis of the utility of culture, biopsy, and direct KOH examination for the diagnosis of onychomycosis. BMC Infect Dis. 2017;17(1):1–11. doi:10.1186/s12879-017-2258-3

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Lim SS, Ohn J, Mun J-H. Diagnosis of onychomycosis: from conventional techniques and dermoscopy to artificial intelligence. Front Med. 2021;8:637216. doi:10.3389/fmed.2021.637216

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