History
Onychomycosis is usually asymptomatic; therefore, patients usually first present for cosmetic reasons without any physical complaints.
As the disease progresses, onychomycosis may interfere with standing, walking, and exercising.
Patients may report paresthesia, pain, discomfort, and loss of dexterity. They also may report loss of self-esteem and lack of social interaction.
A careful history may reveal many environmental and occupational risk factors.
Physical Examination
The subtypes of onychomycosis may be distinguished on the basis of their usual presenting clinical features.
In distal lateral subungual onychomycosis, the nail shows subungual hyperkeratosis and onycholysis, which is usually yellow-white in color. Yellow streaks and/or yellow onycholytic areas in the central portion of the nail plate are commonly observed. Note the images below.
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.
Endonyx onychomycosis presents as a milky white discoloration of the nail plate, but, in contrast to distal lateral subungual onychomycosis, no evidence of subungual hyperkeratosis or onycholysis is present.
White superficial onychomycosis is confined to the toenails and manifests as small, white, speckled or powdery patches on the surface of the nail plate. The nail becomes roughened and crumbles easily. Molds produce a deep variety of white superficial onychomycosis characterized by a larger and deeper nail plate invasion. Note the image below.
Proximal subungual onychomycosis presents as an area of leukonychia in the proximal nail plate that moves distally with nail growth. In proximal subungual onychomycosis caused by molds, leukonychia is typically associated with marked periungual inflammation. Note the image below.
Proximal subungual onychomycosis. Proximal leukonychia. Image courtesy of Dr Antonella Tosti.
Total dystrophic onychomycosis presents as a thickened, opaque, and yellow-brown nail.
In Candida onychomycosis associated with chronic mucocutaneous candidiasis or immunodepression, several or all digits are affected by total onychomycosis associated with periungual inflammation. The digits often take on a bulbous or drumstick appearance. Note the image below.
Candidal onychomycosis in a patient with chronic mucocutaneous candidiasis. Total onychomycosis and paronychia. Image courtesy of Dr Antonella Tosti.
Causes
Onychomycosis is caused by 3 main classes of fungi: dermatophytes, yeasts, and nondermatophyte molds. Dermatophytes are by far the most common cause of onychomycosis. Two major pathogens are responsible for approximately 90% of all onychomycosis cases. Trichophyton rubrum accounts for 70% and Trichophyton mentagrophytes accounts for 20% of all cases. Onychomycosis caused by nondermatophyte molds (Fusarium species, Scopulariopsis brevicaulis,Aspergillus species) is becoming more common worldwide, accounting for up to 10% of cases. [18] Onychomycosis due to Candida is rare. [19]
T rubrum is the most common pathogen in distal lateral subungual onychomycosis. Proximal subungual onychomycosis due to T rubrum infection is typical of immunosuppressed patients . Additionally, Proximal subungual onychomycosis with periungual inflammation is usually caused by molds
White superficial onychomycosis is usually caused by T mentagrophytes; nondermatophyte molds cause deep white superficial onychomycosis.
Candida albicans nail infection is observed in premature children, in immunocompromised patients, and in persons with chronic mucocutaneous candidiasis.
Risk factors for onychomycosis include family history, increasing age, poor health, prior trauma, warm climate, participation in fitness activities, immunosuppression (eg, HIV, drug induced), communal bathing, and occlusive footwear. Biomechanical problems with repetitive microtraumas to the nails cause onycholysis and other nail dystrophies that favor nail invasion by fungi.
Complications
Skin injury adjacent to the nail may allow organisms to colonize, thereby increasing the risk of infectious complications. Reports of complications in elderly persons and persons with diabetes include cellulitis, osteomyelitis, sepsis, and tissue necrosis.
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Distal subungual onychomycosis. Onycholysis and yellow streak. Image courtesy of Dr Antonella Tosti.
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Distal subungual onychomycosis. Subungual hyperkeratosis onycholysis and yellow streak. Image courtesy of Dr Antonella Tosti.
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Proximal subungual onychomycosis. Proximal leukonychia. Image courtesy of Dr Antonella Tosti.
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White superficial onychomycosis. Image courtesy of Dr Antonella Tosti.
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Candidal onychomycosis in a patient with chronic mucocutaneous candidiasis. Total onychomycosis and paronychia. Image courtesy of Dr Antonella Tosti.
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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.
