Onychomycosis Workup

  • Author: Antonella Tosti, MD; Chief Editor: Dirk M Elston, MD   more...
 
Updated: Apr 27, 2012
 

Laboratory Studies

The clinical features of onychomycosis may mimic a large number of other nail disorders. Therefore, laboratory diagnosis of onychomycosis must be confirmed before beginning a treatment regimen. A negative mycological result does not rule out onychomycosis, because direct microscopy may be negative in up to 10% of cases and culture in up to 30% of cases.

Direct microscopy

A 20% potassium hydroxide (KOH) preparation in dimethyl sulfoxide (DMSO) is a useful screening test to rule out the presence of fungi. Before obtaining a specimen, the nails must be clipped and cleansed with an alcohol swab to remove bacteria and debris. The preparation does not require heating or prolonged incubation if DMSO is a component of the KOH solution.

In distal lateral subungual onychomycosis, a specimen should be obtained from the nail bed by curettage. The onycholytic nail plate should be removed and the sample should be obtained at a site most proximal to the cuticle, where the concentration of hyphae is greatest.

In proximal subungual onychomycosis, the overlying nail plate must initially be pared with a No. 15 blade. Then, a sample of the ventral nail plate may be taken. A No. 15 blade may also be used to remove a specimen from the nail surface in white superficial onychomycosis.

Specimens suspected of candidal onychomycosis should be taken from the affected nail bed closest to the proximal and lateral edges.

Nail fragments must be small enough for examination under low power. Large pieces of nail plate may be pulverized prior to microscopy by using a hammer or a nail micronizer. Counterstains, such as chlorazol black E or Parker blue-black ink, may be used to accentuate the hyphae. Shemer et al reported that drilling to obtain specimens and taking the sample from a more proximal site yield better results.[7]

Culture

Direct microscopy cannot identify the specific pathogen involved in onychomycosis. A fungal culture must be used to identify the species of organism.[8] Nondermatophyte molds may be resistant to the conventional therapy used for the more common dermatophytes.[9] Therefore, 2 types of growth medium should be used, one with cycloheximide (dermatophyte test medium [DTM], Mycosel, or Mycobiotic) to select for dermatophytes and one without cycloheximide (Sabouraud glucose agar, Littman oxgall medium, or inhibitory mold agar) to isolate yeasts and nondermatophyte molds.[10]

Cultures should be obtained from pulverized nail scrapings or clippings while the patient has abstained from antifungal medication for at least 2 weeks. The specimen should be kept at room temperature with the cap placed loosely over the inoculated medium.

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Other Tests

Polymerase chain reaction (PCR) assays have been developed to detect fungal DNA from infected nails.[11] A highly sensitive nested PCR assay using species-specific primer pairs based on the 28S ribosomal RNA gene has been developed. This methodology permits detection of both dermatophytes and nondermatophytes.[12]

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Procedures

Dermoscopy is useful to distinguish distal subungual onychomycosis from traumatic onycholysis. In distal subungual onychomycosis, the proximal border of the onycholytic area is jagged owing to the presence of yellow-white spikes that project into the proximal nail plate. See the image below. This patterned has been reported as the "aurora borealis" pattern.[13]

Dermoscopy of distal subungual onychomycosis showiDermoscopy of distal subungual onychomycosis showing irregular margin of the onycholytic area with spikes projecting into the proximal nail plate, reported as the "aurora borealis" pattern. Handyscope at 20X.
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Histologic Findings

Histologic examination of the nail is a very useful alternative to culture or KOH testing. Nail clippings may be sent to the laboratory for diagnosis in a formalin-filled container, or, as a last resort, an incisional nail biopsy (by punch or scalpel) may be performed to help confirm the diagnosis. Staining in the laboratory should be performed with periodic acid-Schiff stain (PAS) or methenamine silver stain to reveal fungal elements. A comparison of diagnostic methods revealed that a nail biopsy and staining with PAS is the most sensitive technique available to diagnose onychomycosis.[14] Examining formalin-fixed, PAS-stained specimens has a higher probability (a higher negative predictive value) than KOH examination in determining that a patient is disease free if the test results are negative.

In addition to excluding other conditions (eg, psoriasis, lichen planus), the topographic distribution, the density, and the nature of the fungal elements may help guide treatment. Biopsy specimens of onychomycosis may show features of psoriasiform hyperplasia, including parakeratosis, thinned rete ridges, narrow suprapapillary plates, and dilated tortuous capillaries. As in direct microscopy, histopathologic diagnosis does not identify the species of causative pathogen.

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Staging

The onychomycosis severity index (OSI) has recently been proposed to grade the severity of distal subungual onychomycosis. The OSI score is obtained by multiplying the score for the area of involvement (range, 0-5) by the score for the proximity of disease to the matrix (range, 1-5). Ten points are added for the presence of a longitudinal streaking or a patch (dermatophytoma) or for greater than 2 mm of subungual hyperkeratosis. Mild onychomycosis corresponds to a score of 1-5; moderate, 6-15; and severe, 16-35.[15]

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Contributor Information and Disclosures
Author

Antonella Tosti, MD  Professor of Dermatology, Department of Dermatology and Cutaneous Surgery, University of Miami, Leonard M Miller School of Medicine

Antonella Tosti, MD is a member of the following medical societies: American Academy of Dermatology, American Dermatological Association, Canadian Dermatology Association, European Academy of Dermatology and Venereology, International Society of Dermatology, and Women's Dermatologic Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Richard K Scher, MD  Adjunct Professor of Dermatology, University of North Carolina; Professor Emeritus of Dermatology, Columbia University

Richard K Scher, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, American Dermatological Association, American Medical Association, Association of Military Surgeons of the US, International Society for Dermatologic Surgery, Noah Worcester Dermatological Society, and Society for Investigative Dermatology

Disclosure: Nothing to disclose.

Richard P Vinson, MD  Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA

Richard P Vinson, MD is a member of the following medical societies: American Academy of Dermatology, Association of Military Dermatologists, Texas Dermatological Society, and Texas Medical Association

Disclosure: Nothing to disclose.

Jeffrey Meffert, MD  Assistant Clinical Professor of Dermatology, University of Texas School of Medicine at San Antonio

Jeffrey Meffert, MD is a member of the following medical societies: American Academy of Dermatology, American Medical Association, Association of Military Dermatologists, and Texas Dermatological Society

Disclosure: Nothing to disclose.

Catherine M Quirk, MD  Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania

Catherine M Quirk, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD  Director, Ackerman Academy of Dermatopathology, New York

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Additional Contributors

The authors and editors of Medscape Referencegratefully acknowledge the contributions of previous authors, Mark Blumberg, MD, MS, Gary R. Kantor, MD, and John Ratz, MD, MBA, to the development and writing of this article.

References

  1. Lubeck DP. Measuring health-related quality of life in onychomycosis. J Am Acad Dermatol. May 1998;38(5 Pt 3):S64-8. [Medline].

  2. Iorizzo M, Piraccini BM, Tosti A. New fungal nail infections. Curr Opin Infect Dis. Apr 2007;20(2):142-5. [Medline].

  3. Kemna ME, Elewski BE. A U.S. epidemiologic survey of superficial fungal diseases. J Am Acad Dermatol. Oct 1996;35(4):539-42. [Medline].

  4. Summerbell RC. Epidemiology and ecology of onychomycosis. Dermatology. 1997;194 Suppl 1:32-6. [Medline].

  5. Gupta AK, Drummond-Main C, Cooper EA, Brintnell W, Piraccini BM, Tosti A. Systematic review of nondermatophyte mold onychomycosis: diagnosis, clinical types, epidemiology, and treatment. J Am Acad Dermatol. Mar 2012;66(3):494-502. [Medline].

  6. Tosti A, Piraccini BM, Lorenzi S, Iorizzo M. Treatment of nondermatophyte mold and Candida onychomycosis. Dermatol Clin. Jul 2003;21(3):491-7, vii. [Medline].

  7. Shemer A, Davidovici B, Grunwald MH, Trau H, Amichai B. Comparative study of nail sampling techniques in onychomycosis. J Dermatol. Jul 2009;36(7):410-4. [Medline].

  8. Elewski BE. Diagnostic techniques for confirming onychomycosis. J Am Acad Dermatol. Sep 1996;35(3 Pt 2):S6-9. [Medline].

  9. Tosti A, Piraccini BM, Lorenzi S. Onychomycosis caused by nondermatophytic molds: clinical features and response to treatment of 59 cases. J Am Acad Dermatol. Feb 2000;42(2 Pt 1):217-24. [Medline].

  10. Elewski BE. Clinical pearl: diagnosis of onychomycosis. J Am Acad Dermatol. Mar 1995;32(3):500-1. [Medline].

  11. Gupta AK, Zaman M, Singh J. Fast and sensitive detection of Trichophyton rubrum DNA from the nail samples of patients with onychomycosis by a double-round polymerase chain reaction-based assay. Br J Dermatol. Oct 2007;157(4):698-703. [Medline].

  12. Ebihara M, Makimura K, Sato K, Abe S, Tsuboi R. Molecular detection of dermatophytes and nondermatophytes in onychomycosis by nested polymerase chain reaction based on 28S ribosomal RNA gene sequences. Br J Dermatol. Nov 2009;161(5):1038-44. [Medline].

  13. Piraccini BM, Balestri R, Starace M, Rech G. Nail digital dermoscopy (Onychoscopy) in the diagnosis of onychomycosis. J Eur Acad Dermatol Venereol. Nov 1 2011;[Medline].

  14. Weinberg JM, Koestenblatt EK, Tutrone WD, Tishler HR, Najarian L. Comparison of diagnostic methods in the evaluation of onychomycosis. J Am Acad Dermatol. Aug 2003;49(2):193-7. [Medline].

  15. Carney C, Tosti A, Daniel R, et al. A new classification system for grading the severity of onychomycosis: Onychomycosis Severity Index. Arch Dermatol. Nov 2011;147(11):1277-82. [Medline].

  16. Piraccini BM, Rech G, Tosti A. Photodynamic therapy of onychomycosis caused by Trichophyton rubrum. J Am Acad Dermatol. Nov 2008;59(5 Suppl):S75-6. [Medline].

  17. Manevitch Z, Lev D, Palhan M, Lewis A, Enk CD. Direct Antifungal Effect of Femtosecond Laser on Trichophyton rubrum Onychomycosis. Photochem Photobiol. Dec 7 2009;[Medline].

  18. Bohn M, Kraemer K. The dermatopharmacologic profile of ciclopirox 8% nail lacquer. J Am Podiatr Med Assoc. Nov-Dec 2000;90(10):491-4. [Medline].

  19. Crawford F, Young P, Godfrey C, et al. Oral treatments for toenail onychomycosis: a systematic review. Arch Dermatol. Jun 2002;138(6):811-6. [Medline].

  20. Gupta AK, Scher RK. Oral antifungal agents for onychomycosis. Lancet. Feb 21 1998;351(9102):541-2. [Medline].

  21. Katz HI, Gupta AK. Oral antifungal drug interactions. Dermatol Clin. Jul 1997;15(3):535-44. [Medline].

  22. Elewski B, Pollak R, Ashton S, Rich P, Schlessinger J, Tavakkol A. A randomized, placebo- and active-controlled, parallel-group, multicentre, investigator-blinded study of four treatment regimens of posaconazole in adults with toenail onychomycosis. Br J Dermatol. Feb 2012;166(2):389-98. [Medline].

  23. Cohen AD, Medvesovsky E, Shalev R, et al. An independent comparison of terbinafine and itraconazole in the treatment of toenail onychomycosis. J Dermatolog Treat. Dec 2003;14(4):237-42. [Medline].

  24. Jennings MB, Pollak R, Harkless LB, Kianifard F, Tavakkol A. Treatment of toenail onychomycosis with oral terbinafine plus aggressive debridement: IRON-CLAD, a large, randomized, open-label, multicenter trial. J Am Podiatr Med Assoc. Nov-Dec 2006;96(6):465-73. [Medline].

  25. Warshaw EM, Bowman T, Bodman MA, Kim JJ, Silva S, Mathias SD. Satisfaction with onychomycosis treatment. Pulse versus continuous dosing. J Am Podiatr Med Assoc. Sep-Oct 2003;93(5):373-9. [Medline].

  26. Zaias N, Rebell G. The successful treatment of Trichophyton rubrum nail bed (distal subungual) onychomycosis with intermittent pulse-dosed terbinafine. Arch Dermatol. Jun 2004;140(6):691-5. [Medline].

  27. Scher RK, Tavakkol A, Sigurgeirsson B, et al. J Onychomycosis: diagnosis and definition of cure. Am Acad Dermatol. 2007;56(6):939-44.

  28. Sigurgeirsson B, Olafsson JH, Steinsson JB, Paul C, Billstein S, Evans EG. Long-term effectiveness of treatment with terbinafine vs itraconazole in onychomycosis: a 5-year blinded prospective follow-up study. Arch Dermatol. Mar 2002;138(3):353-7. [Medline].

  29. Gupta AK, Ryder JE, Johnson AM. Cumulative meta-analysis of systemic antifungal agents for the treatment of onychomycosis. Br J Dermatol. Mar 2004;150(3):537-44. [Medline].

  30. Piraccini BM, Sisti A, Tosti A. Long-term follow-up of toenail onychomycosis caused by dermatophytes after successful treatment with systemic antifungal agents. J Am Acad Dermatol. Mar 2010;62(3):411-4. [Medline].

  31. Bristow IR, Spruce MC. Fungal foot infection, cellulitis and diabetes: a review. Diabet Med. May 2009;26(5):548-51. [Medline].

  32. [Guideline] Frykberg RG, Zgonis T, Armstrong DG, et al. Diabetic foot disorders. A clinical practice guideline (2006 revision). J Foot Ankle Surg. Sep-Oct 2006;45(5 Suppl):S1-66. [Medline].

  33. Gupta AK, Palese CS, Scher RK. How to treat special populations suffering from onychomycosis. Skin and Aging. 1999;7:54-8.

  34. Andre J, Achten G. Onychomycosis. Int J Dermatol. Oct 1987;26(8):481-90. [Medline].

  35. Baran R, Hay RJ, Tosti A, Haneke E. A new classification of onychomycosis. Br J Dermatol. Oct 1998;139(4):567-71. [Medline].

  36. Cribier BJ, Paul C. Long-term efficacy of antifungals in toenail onychomycosis: a critical review. Br J Dermatol. Sep 2001;145(3):446-52. [Medline].

  37. Epstein E. How often does oral treatment of toenail onychomycosis produce a disease-free nail? An analysis of published data. Arch Dermatol. Dec 1998;134(12):1551-4. [Medline].

  38. Evans EG. Causative pathogens in onychomycosis and the possibility of treatment resistance: a review. J Am Acad Dermatol. May 1998;38(5 Pt 3):S32-36. [Medline].

  39. Faergemann J, Baran R. Epidemiology, clinical presentation and diagnosis of onychomycosis. Br J Dermatol. Sep 2003;149 Suppl 65:1-4. [Medline].

  40. Gupta AK, Scher RK, De Doncker P. Current management of onychomycosis. An overview. Dermatol Clin. Jan 1997;15(1):121-35. [Medline].

  41. Gupta AK, Scher RK, De Doncker P, Sauder DN, Shear NH. Onychomycosis. New therapies for an old disease. West J Med. Dec 1996;165(6):349-51. [Medline].

  42. Heikkila H, Stubb S. Long-term results of patients with onychomycosis treated with itraconazole. Acta Derm Venereol. Jan 1997;77(1):70-1. [Medline].

  43. Hull PR. Onychomycosis--treatment, relapse and re-infection. Dermatology. 1997;194 Suppl 1:7-9. [Medline].

  44. Midgley G, Moore MK. Nail infections. Dermatol Clin. Jan 1996;14(1):41-49. [Medline].

  45. Nandedkar-Thomas MA, Scher RK. An update on disorders of the nails. J Am Acad Dermatol. May 2005;52(5):877-87. [Medline].

  46. Odom RB. New therapies for onychomycosis. J Am Acad Dermatol. Sep 1996;35(3 Pt 2):S26-30. [Medline].

  47. Pierard GE, Arrese JE, De Doncker P, Pierard-Franchimont C. Present and potential diagnostic techniques in onychomycosis. J Am Acad Dermatol. Feb 1996;34(2 Pt 1):273-7. [Medline].

  48. Piraccini BM, Lorenzi S, Tosti A. 'Deep' white superficial onychomycosis due to molds. J Eur Acad Dermatol Venereol. Sep 2002;16(5):532-3. [Medline].

  49. Piraccini BM, Tosti A. White superficial onychomycosis: epidemiological, clinical, and pathological study of 79 patients. Arch Dermatol. Jun 2004;140(6):696-701. [Medline].

  50. Scher RK. Onychomycosis: a significant medical disorder. J Am Acad Dermatol. Sep 1996;35(3 Pt 2):S2-5. [Medline].

  51. Scher RK, Baran R. Onychomycosis in clinical practice: factors contributing to recurrence. Br J Dermatol. Sep 2003;149 Suppl 65:5-9. [Medline].

  52. Scher RK, Coppa LM. Advances in the diagnosis and treatment of onychomycosis. Hosp Med. 1998;34(4):11-20.

  53. Tosti A, Piraccini BM, Stinchi C, Colombo MD. Relapses of onychomycosis after successful treatment with systemic antifungals: a three-year follow-up. Dermatology. 1998;197(2):162-6. [Medline].

  54. Zaias N. Onychomycosis. Arch Dermatol. Feb 1972;105(2):263-74. [Medline].

 
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Distal subungual onychomycosis. Onycholysis and yellow streak. Image courtesy of Dr Antonella Tosti.
Distal subungual onychomycosis. Subungual hyperkeratosis onycholysis and yellow streak. Image courtesy of Dr Antonella Tosti.
Proximal subungual onychomycosis. Proximal leukonychia. Image courtesy of Dr Antonella Tosti.
White superficial onychomycosis. Image courtesy of Dr Antonella Tosti.
Candidal onychomycosis in a patient with chronic mucocutaneous candidiasis. Total onychomycosis and paronychia. Image courtesy of Dr Antonella Tosti.
Dermoscopy of distal subungual onychomycosis showing irregular margin of the onycholytic area with spikes projecting into the proximal nail plate, reported as the "aurora borealis" pattern. Handyscope at 20X.
 
 
 
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