MedicineToday 2014; 15(12): 40-44 PEER REVIEWED FEATURE 2 CPD POINTS Nail disease Is it fungal and how should it be managed? Key points KENG-EE THAI MB BS(Hons), BMedSci(Hons), FACD • Onychomycosis is typically asymptomatic and Fungal infection accounts for about half of all nail abnormalities. subclinical, representing a Differential diagnoses include psoriasis, lichen planus and Pseudomonas cosmetic problem. infection. Treatment usually requires long-term continuous or pulsed • Dermatophyte moulds are the most common cause. antifungal therapy. • Differential diagnoses that should be considered in ungal infection of the fingernail or toenail DERMATOPHYTE VS NONDERMATOPHYTE patients with nail plate is termed onychomycosis or tinea MOULDS abnormalities include unguium. It accounts for about one-third Most cases of onychomycosis are caused by psoriasis, lichen planus and of all fungal infections and half of all nail dermatophyte moulds. These fungi are Pseudomonas infection. F abnormalities. Onychomycosis has a prevalence ubi quitous; they are found in almost any • Keeping the feet and of about 10%, varying geographically. The environment that can support their existence. toenails dry can help prevalence increases with age. It is mostly Dermatophytes grow on keratinised tissues – prevent onychomycosis. asymptomatic and subclinical; patients present the ‘dead’ component of skin and its append- • Systemic agents have the only when affected by its clinical appearance. ages. The most common dermatophyte highest success rates in However, onychomycosis can be the source of infecting nails and skin is Trichophyton treating onychomycosis; dermatophytes that cause tinea on other parts rubrum. This anthropophilic organism has a they include terbinafine, of the body. Treatment typically requires a worldwide distribution and is abundant in any itraconazole and protracted course of an oral antifungal agent. moist, warm area frequented by humans. Other fluconazole. This article outlines a practical approach to dermatophyte species can also affect the nail • Topical treatments are the management of onychomycosis. The phar- plate. Dermatophyte infections are typically typically useful only for macology of topical and oral antifungal agents easier to treat than nondermatophyte infec- superficial white used in dermatology was discussed in a previous tions, as most respond to oral antifungal onychomycosis and very article on dermatophyte infections, in the June preparations. mild subungual 2014 issue of Medicine Today.1 Saprophytic nondermatophyte moulds onychomycosis; they include amorolfine, Dr Thai is a Consultant Dermatologist and Visiting Medical Officer at the Epicutaneous Patch Testing Clinic and Hair bifonazole, ciclopiroxCopyright and _Layoutand 1 Nail17/01/12 Clinic, Prince 1:43 PM of Wales Page Hospital, 4 Sydney; a Visiting Medical Officer at the Macquarie University Hospital, miconazole. Sydney; and in private practice in Gordon, Sydney, NSW. © BODELL COMMUNICATIONS/PHOTOTAKE/DIOMEDIA.COM 40 MedicineToday x DECEMBER 2014, VOLUME 15, NUMBER 12 Downloaded for personal use only. No other uses permitted without permission. © MedicineToday 2014. Figure 2. Classic distal and lateral subungual onychomycosis involving multiple toe and finger nails. Note the yellow-green Figure 1. Superficial white onychomycosis, showing a powdery discolouration visible on the surface of the nail, representing tinea white infection of the superficial part of the nail plate of the in the nail plate and subungual hyperkeratosis, and onycholysis of second toe. the fingernails, in contrast with the normal fingernail. can also infect the nail plate, albeit uncom- Distal and lateral subungual monly. Typically, these moulds do not grow onychomycosis on other keratinised tissues, such as the Distal and lateral subungual onychomycosis is skin. Scopulariopsis brevicaulis is the most the most common type of onychomycosis, with common nondermatophyte to infect the the infection gaining access via the distal free undamaged nail plate, whereas Acremonium, nail plate and extending proximally (Figure 2). Aspergillus and Fusarium spp. can cause Yellow, brown or white discolouration of the superficial white onychomycosis. Infections nail plate occurs. The nail plate may thicken and with nondermatophyte moulds are often is lifted up by subungual hyperkeratosis as the more difficult to treat than dermatophyte infection moves upwards. Chards (streaks) of infections, especially if deep-seated; itracona- infection can be seen running up the nail plate. zole with or without nail plate avulsion is Eventually the nail plate can be completely required. involved and destroyed. Distal and lateral In addition, Candida spp. can infect the nail subungual onychomycosis may start in the nail plate and associated nail fold. Infection can plate of one digit and extend to the others. take the form of paronychia and associated nail dystrophy or, more rarely, total nail plate Proximal subungual onychomycosis involvement and destruction in the setting of Proximal subungual onychomycosis is unusual, chronic mucocutaneous candidiasis. where whitening of the nail starts proximally as the fungus is able to access the nail plate via PRESENTATION the proximal nail fold. Proximal subungual There are several types of onychomycosis, based onychomycosis is more common in patients on the mechanism of infection and clinical who are immunosuppressed, such as in HIV appearance of the nail plate. infection. T. rubrum is the most common cause. Superficial white onychomycosis Superficial white onychomycosis describes a Endonyx onychomycosis very superficial infection, where the fungal Endonyx onychomycosis is a highly unusual elements are found on the surface of the nail variant, where the nail plate becomes second- plate. Powdery, white, circumscribed patches arily involved by an infection that begins in the are seen (Figure 1). This is typically caused by finger or toe pulp. Extension of the infection to Trichophyton interdigitaleCopyright. T. _Layoutrubrum 1 and 17/01/12 non- 1:43the PMnail Page plate 4 leads to nail pits, lamellar splits, dermatophytes can also be causative. subungual hyperkeratosis and onycholysis. MedicineToday x DECEMBER 2014, VOLUME 15, NUMBER 12 41 Downloaded for personal use only. No other uses permitted without permission. © MedicineToday 2014. FUNGAL NAIL DISEASE CONTINUED Figure 3. Nail psoriasis Figure 4. showing subungual Pseudomonas hyperkeratosis, which is infection of the commonly misdiag nosed nail plate as tinea. Note the absence showing a of the yellow-green streaks greenish expected in dermatophyte discolouration infection, and the presence that is not seen of the salmon-pink ‘oil in tinea. drop’ sign just proximal to the hyperkeratosis. Endonyx onychomycosis is caused by fun- or nail destruction, although an accompa- INVESTIGATIONS FOR ONYCHOMYCOSIS gal species responsible for endothrix infec- nying chronic paronychia may lead to nail The ‘gold standard’ for the laboratory tion (infection of the substance of the hair plate distortion or dystrophy. diagnosis of onychomycosis is a positive shaft), such as Trichophyton soudanense. fungal culture of nail clippings. Although Lichen planus isolation of a fungus is diagnostic, culture DIFFERENTIAL DIAGNOSES Lichen planus is an inflammatory condi- is an insensitive test, and a negative result Although onychomycosis is exceedingly tion that leads to destruction of the nail does not rule out onychomycosis. When common and in most circumstances easy complex. The characteristic feature is a a nail specimen is harvested for micro- to diagnose, several differential diagnoses pterygium. In the context of the nail appa- scopy and culture, the greater the volume should always be considered. It is also ratus, this is a scarring process in which of material submitted the greater the important to note that onychomycosis the proximal nail fold adheres to the nail chance of a positive culture. The soft, can be a secondary infection or coexist plate and is dragged along as the nail macerated subungual debris gives the with any other nail dystrophy. grows. The end product is a scarred nail greatest load of fungal elements. A small bed with no nail plate. (2 mm) bone or skin curette is useful for Psoriasis scraping underneath the nail plate. Psoriasis can cause nail dystrophy and Simple traumatic onycholysis Fungal elements can also be seen on discolouration, subungual hyperkeratosis Simple traumatic onycholysis is very com- histopathology of the nail plate and are and onycholysis. It can be very difficult mon. In the fingernails, this is caused by easily identified by the periodic acid-Schiff to differentiate clinically from onycho- excessive wet work and hand washing, as stain. This method can have a much mycosis. However, features of psoriasis well as fastidious nail care where the higher positivity rate for diagnosis of that help in this differentiation include: patient cleans under the nail to remove onychomycosis, but the disadvantage is • a different quality of the dystrophic debris, inadvertently lifting the nail the lack of culture confirmation. nail, with less yellow discolouration further. The toenails can be lifted by exces- and no white/yellow streaks sive walking and exercise in tight shoes. PREVENTION • early involvement of multiple nails Scraping of the great toenail along the General measures • changes such as distinctive nail pits in ceiling of the toe box of the shoe can shear Dermatophytes are ubiquitous organ- a regular pattern