Management of Onychomycosis

Y. Poulin, MD

Department of Medicine (Dermatology), Laval University, Quebec City, Quebec, Canada

What is Onychomycosis?

• The colonisation/ infection of the nails by fungi
• Most often seen on toenails, mainly the big toenail
• Infection of fingernails is almost never seen without associated toenail involvement.

Why is It Important?

• Nail dystrophy can be uncomfortable or painful.
• It can be unsightly causing embarrassment.
• Nail fungus can be a reservoir for infection of feet, groin, trunk and other areas.
• Can be a source for chronic tinea pedis and other types of tinea (e.g., cruris, corporis).
  – increases risk of complications such as foot cellulitis
  – increases risk of idiopathic reaction with eczema on the feet and hands.

Risk Factors for Onychomycosis

• 6.9% of Canadians have onychomycosis.[Gupta AK, et al. J Am Acad Dermatol 43(2 pt1):244-8 (2000)]
• It is uncommon in children.
• Most prevalent in patients with
  – advanced age
  – diabetes
  – peripheral vascular disease
  – immunosuppression
  – trauma to nails (e.g., runners often experience nail trauma)
  – not to be confused with nail dystrophy of runners
  – occupations requiring occlusive foot wear.

How to Recognize Onychomycosis

Nail changes include:

• Nail discoloration
  • on the surface of nail
  • white superficial onycholysis
  • on the nail itself or subungual changes.
• Onycholysis
  • separation of nail from nail pad.
• Subungual hyperkeratosis
  • distal nail
  • lateral nail
  • proximal nail.
• Nail thickening and crumbling.

Although nail dystrophy may be due to various causes, fungal invasion is found in more than 50% of cases. Other causes of nail dystrophy include mechanical trauma (the fifth toenail is very frequently distorted by chronic trauma) and psoriasis although the differential diagnosis is extensive.

Onycholysis may be due to various factors, as is thickening of nails (see below). Nail pitting and the oil-drop sign (spotty yellow-brown discoloration of the nail) are specific to psoriasis. Of note, psoriatic nails and distorted nails from trauma may become infected by fungi.

Causes of Onycholysis

• Psoriasis
• Trauma
• Hyperhidrosis
• Eczema
• Chemical (e.g., solvents, nail hardeners)
• Drug-induced:
  – photo-onycholysis (with doxicycline and other photosensitizers)
  – chemotherapy.
• Impaired peripheral circulation
• Systemic disorders
  – hypo- and hyperthyroidism
  – porphyrias.
• Idiopathic
• Onychomycosis

Causes of Nail Thickening

• Onychomycosis
• Psoriasis
• Eczema
• Trauma
• Yellow nail syndrome
• Other rare causes

Diagnosis of Onychomycosis

• Diagnosis should be confirmed by
  – direct microscopic examination of nail clippings
  – culture.
• Procedures are simple.
• Results will guide the treatment.
• Some fungal strains are especially hard to treat.
• Nail clippings should include the full thickness of the nail plate.
• One positive culture/identification of fungus out of three consecutive samples is necessary for diagnosis.

Treatment of Onychomycosis

Patients with onychomycosis should be treated unless they are of advanced age or there are contraindications to available therapies.

White superficial onychomycosis	Mild distal subungual hyperkeratosis	Moderate distal hyperkeratosis	Lateral subungual hyperkeratosis	Proximal subungual hyperkeratosis
Topical treatment	Topical or systemic treatment	Systemic +/- topical
Topical treatment can be used to control the spread of the infection and as an adjunct to systemic treatment. Removal of dermatophytomas (densely packed hyphae forming subungual masses) is advised. Nail removal is not recommended unless there are unusual circumstances.

Systemic Treatments

The most often prescribed systemic treatments are terbinafine and itraconazole, the former being because it generally has a higher cure rate. Fluconazole is seldom used.

Terbinafine

Terbinafine 250mg is given daily for 12 weeks. Pretreatment serum transaminase (ALT, AST) tests are advised as a baseline for all patients before taking terbinafine tablets. These tests should be repeated after 3 weeks of treatment to check for hepatic toxicity.

Itraconazole

Itraconazole is mainly given in pulses of 7 days, e.g., 200mg b.i.d. x 7 days at week 1, week 5 and week 9 for a total of 3 pulses over 3 months. Itraconazole must be taken immediately after a full meal. Azole compounds have multiple drug interactions that must be addressed before starting the treatment.

Topical Treatment

Ciclopirox Nail Lacquer

Topical ciclopirox 8% nail lacquer is to be applied once daily for 48 weeks and nail debridement should be performed by a health professional.

The active ingredient penetrates as deep as 0.4mm into the nail after one application.[Bohn M, et al. J Am Podiatr Med Assoc 90:491-4 (2000)]

A meta-analysis of 10 trials disclosed a mean mycological cure rate of 52.6%
with this topical treatment.[Gupta AK, et al. J Am Acad Dermatol 43(4 Suppl):S70-80 (2000)] Ciclopirox nail lacquer is the only Health Canada approved topical treatment with proven efficacy.

Systemic and Topical Combination

Oral terbinafine may be advantageously combined with topical ciclopirox nail lacquer. In a recently published trial, the mycological cure rate was 56% for patients receiving 12 weeks of oral terbinafine alone and 70.4% for patients treated with a combination of oral terbinafine for 12 weeks plus daily ciclopirox nail lacquer for 48 weeks.[Gupta AK. J Drugs Dermatol 4:481-5 (2005).]

Conclusion

Diagnosis of onychomycosis can only be established with a positive culture or observation of fungus in the nail clippings. Consideration should be given to cost and possible complications before starting treatment. Recurrent disease is a problem even after a complete cure.