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A 5-year-old boy presents to his physician for evaluation of "toenail issues" for at least 1 year. The family has noticed changes of his right great toenail, which they thought might be due to "tight shoes," stating that the boy has been growing out of his shoes quickly. In the last 6 months, his mother has noted a "crumbly" nail with yellow discoloration. There has been no prior treatment, although his parents now are replacing his sneakers more regularly to allow him "room to grow." He has no history of toe swelling or pain.

He is otherwise healthy, and he has no history of psoriasis or eczema. He has had no significant viral infections, although some children in his school did have hand, foot, and mouth disease several months ago. His mother states that her husband has athlete's foot, which has been treated with "creams and sprays."

Physical exam

The toenail of the right foot great toe has thickening of the distal part of the nail, with onycholysis (separation of the nail plate from the nail bed), yellow discoloration, and subungual debris. The right toe shows some chronic dystrophy. Other toenails appear normal, and the skin of the feet is otherwise unremarkable.

What is your primary diagnosis?

A. Traumatic onychodystrophy

B. Nail psoriasis

C. Lichen planus

D. Onychomycosis

E. Onychomadesis

Onychomycosis is a nail infection caused by a variety of fungi, including dermatophytes, yeasts, and nondermatophyte molds. Tinea unguium refers specifically to nail infections caused by dermatophytes, which are the most common cause of onychomycosis; they cause 82% of cases in the U.S. hospital population. (1)

Onychomycosis is more prevalent in adults than in the pediatric population. (2) A recent study showed that 3.22%, 0.40%, and 0.37% of adults have culture-proven dermatophyte, yeast, and nondermatophyte mold onychomycosis, respectively, while in the pediatric population, 0.14% have dermatophyte and 0.09% have yeast toenail onychomycosis. (2)

The likely reason for lower prevalence of onychomycosis in the pediatric population is the faster growth rate of pediatric nails, the smaller surface area susceptible to infection, and the absence of cumulative trauma and tinea pedis. (2) Distal lateral subungual onychomycosis is the most common clinical pattern of onychomycosis. (2)

The diagnosis usually is based on strong clinical suspicion, but laboratory evidence to support a clinical diagnosis is ideal. Patients may be evaluated with a fungal culture, potassium hydroxide (KOH) preparation, or histologic evaluation of the nail clippings with periodic acid-Schiff (PAS) staining. A KOH preparation is highly specific for onychomycosis, but sensitivity depends on the specimen obtained. The histopathology of the nail clippings sample treated with a PAS stain demonstrates fungal elements and is the most sensitive test, but it does not identify the species. (3) It takes a few days for the results and costs more than a KOH preparation.


Differential diagnosis

The differential for nail dystrophy in children includes trauma, fungal infection, congenital dystrophies, psoriasis, and lichen planus. (4)

Trauma can result in similar changes to onychomycosis, such as distal onycholysis. Unlike the most common type of onychomycosis, there is rarely distal thickening of the nail. Usually the morphology, history of trauma, and culture can be used to differentiate the two.

Congenital dystrophies often include diseases that have other clinical manifestations. Children exhibited nail alterations in diseases such as dystrophic epidermolysis bullosa, focal dermal hypoplasia, Turner syndrome, and Down syndrome. (4)

"Twenty-nail dystrophy," also known as trachyonychia, presents with longitudinal ridges, lost of luster, sandpaper-like rough appearance, and pitting. While the cause is not known, it may be associated with lichen planus, psoriasis, alopecia areata, and atopic dermatitis.

Nail psoriasis can present similarly to onychomycosis with subungual hyperkeratosis and onycholysis. However, distinguishing features for nail psoriasis include pitting, nail bed salmon patches (areas of yellow or pink discoloration), or "oil drop" discoloration, and other systemic findings such as cutaneous or joint findings.

Lichen planus is an inflammatory condition of unknown etiology that also can present with onycholysis with or without subungual hyperkeratosis when it involves the nail matrix. Its clinical characteristics include longitudinal ridging, nail plate thinning, and longitudinal fissuring.

Onychomadesis is the proximal separation of the nail plate from the nail matrix and bed. It is caused by temporary arrest of the nail matrix activity associated with a variety of systemic illnesses or drug exposure, and presents with "peeling" or shedding of the nail from the proximal portion of the plate. It has been noticed commonly with hand, foot, and mouth disease in children.


The term dermatophytosis describes infections caused by members of the genera Microsporum, Trichophyton, and Epidermophyton. Trichophyton rubrum is the most common dermatophyte to cause onychomycosis. (1)

Risk factors for developing onychomycosis include older age, tinea pedis, psoriasis, diabetes, immunodeficiency, genetic predisposition, swimming, and living with family members who have onychomycosis. (5) Tinea pedis is a major risk factor for the development of onychomycosis, with concurrent rates of the two diseases reported as high as 47%. (6) Candida species may cause onychomycosis, while nondermatophyte molds (such as Acremonium, Alternaria, Aspergillus, Fusarium, Scytalidium, and Scopulariopsis species) are rarely true pathogens in immunocompetent children. (2)


Onychomycosis may cause physical discomfort and pain, and may increase the risk for developing bacterial cellulitis, especially in patients with tinea pedis. (7) Treatment options can include observation, if there is minimal discomfort, oral systemic antifungal medications, topical antifungal medications, and physical interventions.

While there is no systemic antifungal approved by the Food and Drug Administration for use in children, several systemic antifungals may be utilized off label. Oral terbinafine or itraconazole are the most effective in achieving cure, with griseofulvin next most effective and fluconazole less so. (8) The safety and effectiveness of these medications in children have not been established. With the exception of one case of ataxia with the use of itraconazole, adverse events for terbinafine and itraconazole treatment in children are limited to reports listed in the prescribing information and include: gastrointestinal side effects, urticaria, hepatotoxicity, neutropenia, thrombocytopenia, and cytochrome P450 enzyme inhibition. (8) Terbinafine dosing for children is based on studies for tinea capitis and determined by weight: 10-20 kg, 62.5 mg/day; 20-40 kg, 125 mg/day; greater than 40 kg, 250 mg/day for 6 weeks. (9) FDA prescribing information suggests a baseline liver function panel prior to initiation of the drug, but there are no recommendations on serial lab monitoring. Dosing of itraconazole in the pediatric population is not as well established. (9)

Topical antifungal agents can be used in pediatric nail infections that do not involve the nail matrix (lunula). Pediatric nails grow faster than adult nails and children have a thinner nail plate, which may allow better penetration of the drug, making children more likely to respond better to topical treatment. (10) Topical therapy options for onychomycosis include ciclopirox and amorolfine nail lacquers, and bifonazole-urea; these require application for prolonged periods of time. Friedlander et al. showed that children with onychomycosis without nail matrix treated with ciclopirox 8% over 32 weeks had a 90% mycologic cure rate. (11) Recently, new topical treatments (efinaconazole and tavaborole) became available for treatment of onychomycosis in adults and appear to be more effective. (12,13) The data for these treatments in pediatric onychomycosis are being gathered, and the results will provide insight into the efficacy of these new formulations in the pediatric population.

Behavioral measures that may reduce risk of onychomycosis include keeping feet cool and dry, wearing shoes in public areas, and avoidance of shared, unsterilized nail manicure equipment. (5)


(1.) J Eur Acad Dermatol Venereol. 2014 Nov;28(11): 1480-91.

(2.) J Eur Acad Dermatol Venereol. 2015 Jun;29(6): 1039-44.

(3.) J Eur Acad Dermatol Venereol. 2011 Feb;25(2):235-7.

(4.) Pediatr Dermatol. 2001 Mar;18:107-9.

(5.) J Drugs Dermatol. 2015 Oct;14(10 Suppl):s32-4.

(6.) J Am Acad Dermatol. 1997 Mar;36(3 Pt l):395-402.

(7.) Dermatology. 2004;209(4):301-7.

(8.) Pediatr Dermatol. 2013 May-Jun;30(3):294-302.

(9.) Tinea Pedis and Tinea Unguium, in "Red Book: 2015 Report of the Committee on Infectious Diseases, 30th Edition (Elk Grove Village, 1L: American Academy of Pediatrics, 2015;784-6).

(10.) Am J Clin Dermatol. 2014 Dec;15(6):489-502.

(11.) Pediatr Dermatol. 2013 MayJun;30(3):316-22.

(12.) J Am Acad Dermatol. 2015 Jul;73(1):62-9.

(13.) J Am Acad Dermatol. 2013 Apr;68(4):600-8.


Dr. Eichenfield is chief of pediatric and adolescent dermatology at Rady Children's Hospital-San Diego and professor of dermatology and pediatrics at the University of California, San Diego.

Ms. Borok is a medical student at the University of California, Los Angeles. Dr. Eichenfield and Ms. Borok said they had no relevant financial disclosures.

Caption: The toenail of the right foot great toe has thickening of the distal part of the nail, with onycholysis, yellow discoloration, and subungual debris.
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Title Annotation:Pediatric Dermatology Consult
Author:Eichenfield, Lawrence F.; Borok, Jenna
Publication:Pediatric News
Date:Sep 1, 2016
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