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onychomycosis

Etiology: 1) dermatophytes (Tinea unguium) a) Trichophyton rubrum 90% [4] b) Microsporum canis (rare) [4] 2) Candida infects fingernails in patients chronically exposed to water [4] 3) Fusarium [3] Epidemiology: - more common in older men with comorbidities - age itself is a risk factor - diabetes mellitus, immunosuppression - poor hygiene may contribute, but is not a major risk factor - peripheral arterial disease not a risk factor [4] Pathology: - dermatophytosis of distal nail plate Clinical manifestations: 1) thickening (hypertrophy, onychauxis) & discoloration (yellow, white, brown) of nail 2) erosion with pitting & yellow-white crumbling debris 3) onycholysis: - scaling under elevated distal free edge of the nail plate 4) subungual hyperkeratosis [15] 5) sometimes dermatophyte invades surface of toenail & presents as a white crust [3] 6) most patients are asymptomatic 7) painful [3,4] * images [12,13] Laboratory: 1) 10% KOH preparation a) hyphae of Trichophyton b) budding or microspores 2) culture of nail & debris on Sabouraud's agar 3) periodic acid-Schiff base staining of nail clipping is more sensitive than KOH preparation or culture (~85%) [3] Differential diagnosis: 1) psoriasis a) more pitting of nail with psoriasis b) periungual inflammation c) skin manifestations of psoriasis 2) traumatic nail dystrophy 3) lichen planus [3] - can affect the nails in about 10% of cases - causes nail plate dystrophy, including longitudinal roughness & ridging, nail thinning, red-streaking, & scarring of the proximal nail fold & matrix 4) paronychia: - infection of the nail fold, painful or tender swelling of the nail fold 5) periungual redness may also be seen with Candida infection 6) peripheral vascular disease [3] 7) aging [3] * < 50% of nail dystrophies associated with fungal infection Complications: - neuropathic ulceration of nailbed [4] Management: 1) confirm diagnosis prior to treatment a) most patients are asymptomatic & do not require treatment b) obtain culture or microscopic confirmation prior to treatment [3] c) up to 50% of nail dystrophies are caused by disorders other than fungal infection (see differential diagnosis) d) asymptomatic patients with diabetic neuropathy or arterial insufficiency are predisposed to cellulitis & might warrant treatment [3] 2) prolonged treatment 3) frequent recurrence (50% at best) [2] 4) topical antifungals do not penetrate nail bed a) ciclopirox (Penlac nail lacquer) FDA approved in 2000 for topical treatment of Trichophyton rubrum - 12% success rate (onychomycosis) after 1 year of daily use [2] b) Lotrimin, Loprox, tea tree oil used but little evidence of effectiveness [2] c) Vicks VapoRub & bleach have been advertised as treatment on the internet, but no proof of effectiveness - Vicks VapoRub may be of benefit [9] d) efinaconazole (Jublia) 10% solution - once daily for 48 weeks (complete cure: 15-18% vs 3% for placebo) [6] e) tolnaftate 1% - Fungi Cure (OTC) unsbstantiated claims of efficacy - Tinactin another tolnaftate 1% OTC is not indicated for onychomycosis 6) systemic therapy is mainstay of treatment a) terbinafine* (Lamisil) recommended in GRS10 1] 250 mg PO QD a] 6 weeks (fingernails) b] 12 weeks (toenails) 2] pulse dose: 500 mg PO QD for 1st week of month a] 2 months for fingernails b] 4 months for toenails b) itraconazole# 200 mg PO BID for 1st week of the month 1] 3 months for fingernails 2] 4 months for toenails c) fluconazole 150-300 mg weekly for 6-12 months [3] d) griseofulvin 750-1000 mg QD in divided doses (TID/BID) 1] 6-12 months for fingernails 2] 18 months for toenails 3] initial monitoring for neutropenia & liver function 4] does NOT work well; NOT recommended [2] e) ketoconazole 200 mg/day a] monitor for hepatotoxicity b] NOT recommended [2] 7) nail evulsion: topical application of 30% salicylic acid, 40% urea or 50% KI to soften nail 8) surgical removal of nail 9) Nd:YAG laser & fractional CO2 laser in combination with topical treatment may be of some benefit [11] * drug of choice, 50% long-term success [2] not clear whether pulse dose as effective as continuous dose GRS10 suggests onychomycosis is not benign & needs to be treated [4] terbinafine is recommended treatment [4[ # 2nd best drug; pulse dose as effective as continuous dose

General

mycosis; fungal infection nail disease

References

  1. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996. pg 983
  2. Onychomycosis: Review of Treatment Options Prescriber's Letter 11(4):21 2004 Detail-Document#: 200405 (subscription needed) http://www.prescribersletter.com
  3. Medical Knowledge Self Assessment Program (MKSAP) 15, 16, 18, 19. American College of Physicians, Philadelphia 2009, 2012, 2018, 2022. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  4. Geriatric Review Syllabus, 7th edition Parada JT et al (eds) American Geriatrics Society, 2010 - Geriatric Review Syllabus, 8th edition (GRS8) Durso SC and Sullivan GN (eds) American Geriatrics Society, 2013 - Geriatric Review Syllabus, 10th edition (GRS10) Harper GM, Lyons WL, Potter JF (eds) American Geriatrics Society, 2019
  5. Prescriber's Letter 20(5): 2013 Comparison of Pharmacotherapy for Onychomycosis Detail-Document#: 290509 (subscription needed) http://www.prescribersletter.com
  6. Elewski BE et al. Efinaconazole 10% solution in the treatment of toenail onychomycosis: Two phase III multicenter, randomized, double- blind studies. J Am Acad Dermatol 2013 Apr; 68:600 PMID: 23177180
  7. Welsh O, Vera-Cabrera L, Welsh E. Onychomycosis. Clin Dermatol. 2010 Mar 4;28(2):151-9 PMID: 20347657
  8. de Berker D. Clinical practice. Fungal nail disease. N Engl J Med. 2009 May 14;360(20):2108-16 PMID: 19439745
  9. Derby R1, Rohal P, Jackson C, Beutler A, Olsen C. Novel treatment of onychomycosis using over-the-counter mentholated ointment: a clinical case series. J Am Board Fam Med. 2011 Jan-Feb;24(1):69-74 PMID: 21209346
  10. Gupta AK, Uro M, Cooper EA. Onychomycosis therapy: past, present, future. J Drugs Dermatol. 2010 Sep;9(9):1109-13. PMID: 20865843
  11. Alam M Does Laser Work for Treating Onychomycosis? Maybe, Sometimes. NEJM Journal Watch. Aug 28, 2014 Massachusetts Medical Society (subscription needed) http://www.jwatch.org - Hollmig ST et al. Lack of efficacy with 1064-nm neodymium:yttrium-aluminum- garnet laser for the treatment of onychomycosis: A randomized, controlled trial. J Am Acad Dermatol 2014 May 15; 70:911. PMID: 24641985 - Lim E-H et al. Toenail onychomycosis treated with a fractional carbon-dioxide laser and topical antifungal cream. J Am Acad Dermatol 2014 May 15; 70:918 PMID: 24655819
  12. Tosti A, MD; Elston RM (images) Medscape: Onychomycosis http://emedicine.medscape.com/article/1105828-overview
  13. DermNet NZ. (images) Fungal nail infections (onychomycosis) http://www.dermnetnz.org/fungal/onychomycosis.html
  14. Lipner SR, Scher RK. Onychomycosis: Clinical overview and diagnosis. J Am Acad Dermatol. 2019 Apr;80(4):835-851. PMID: 29959961 Review.
  15. Leung AKC, Lam JM, Leong KF et al Onychomycosis: An Updated Review. Recent Pat Inflamm Allergy Drug Discov. 2020;14(1):32-45 PMID: 31738146 PMCID: PMC7509699 Free PMC article. Review.