What is Tinea unguium?
- The term tinea unguium refers to dermatophyte infections of the fingernails or toenails.
- Onychomycosis is a less specific term used to describe fungal disease of the nails.
- In addition to dermatophytes, it can be caused by a number of other moulds and by Candida species.
- This condition is common in men and older adults and is seen more in people with weakened immune system such as individuals with diabetes, psoriasis, peripheral vascular disease.
- Geographical distribution:
- Distributed worldwide.
Epidemiology of Tinea unguium:
- Etiology:
- Onychomycosis is the most usual nail disease in adults, responsible for up to 50% of all nail diseases.
- The most commonly asssociated dermatophyte is the anthropophilic species, Trichophyton rubrum, followed by T. mentagrophytes var. interdigitale.
- Onychomycosis is most prevalent in older adults but, due to the limited number of large-scale studies, the actual incidence of the condition is difficult to assess.
- Various risk factors for onychomycosis have been identified. They include:
– male gender
– increasing age peripheral vascular disease
– hyperhidrosis
– tinea pedis and dystrophic nails - The difference between the incidence of onychomycosis in men and women might be a reflection of the degree to which individuals are concerned about the appearance of their nails.
- Likewise the higher incidence of onychomycosis in older individuals could be due to the greater likelihood of younger patients seeking treatment at an earlier stage.
Clinical manifestations of Tinea unguium:
- There are four identified clinical patterns of dermatophyte onychomycosis:
- distal and lateral subungual onychomycosis
- superficial white onychomycosis
- proximal subungual onychomycosis
- total dystrophic onychomycosis
- It is very rare to see a patient with finger- nail infection without toenail involvement.
- Distal and lateral subungual disease:
- It is the most common presentation.
- The affected nail becomes thickened and discoloured, with a varying degree of onycholysis (separation of the nail plate from the nail bed).
- Toenails are more commonly affected than fingernails.
- The infection of toenails is usually secondary to tinea pedis, whereas fingernail infection generally follows tinea manuum, tinea capitis or tinea corporis.
- Tinea unguium may infect a single nail, more than one nail, both fingernails and toenails, or in exceptional circumstances, all of them.
- The first and fifth toenails are more frequently affected, probably because footwear causes more damage to these nails.
- Fingernail infections are usually unilateral.
2. Superficial white onychomycosis:
- The infection initiates at the superficial layer of the nail plate and migrates to the deeper layers.
- Crumbling white lesions is seen on the nail surface, especially the toenails.
- These slowly spread until the entire nail plate is engaged.
- This condition arises normally due to Trichophyton mentagrophytes var. interdigitale infection.
3. Proximal subungual onychomycosis:
- Most cases of proximal subungual onychomycosis involve the toenails.
- This infection originates in the proximal nail fold, with subsequent penetration into the newly forming nail plate.
- The distal region of the nail stays normal until late in the course ofthe disease. T. rubrum is often the cause.
- Although proximal subungual onychomycosis is the least common presentation of dermatophyte nail infection in the general population, it is common in persons with the acquired immunodeficiency syndrome (AIDS).
- It has sometimes been considered a useful marker of human immunodeficiency virus (HIV)infection.
- In AIDS patients, the infection often spreads rapidly from the proximal margin and upper surface of the nail to produce gross white discoloration of the plate without obvious thickening.
4. Total dystrophic onychomycosis:
- These different clinical forms of nail disease may eventually lead to total dystrophic onychomycosis, in which the whole of the nail bed and nail plate is involved.
- The pattern of infection is variable.
- In occasional cases, pockets of tightly packed hyphae develop in the subungual space leading to a dense white lesion visible beneath the nail.
- The type of infection can be resistant to antifungal treatment without prior removal of the lesion.
- This appearance is most often seen in the great toenail.
- In total dystrophic onychomycosis, the infected nail generally begins to lift up from the nail bed due to an accumulation of debris (hyperkeratosis) under the nail.
- The nail becomes thickened and yellow or brown in colour.
- The nail plate may crumble, beginning at the free end.
- The infection may be confined to only one nail, but more commonly several nails on one or both feet are affected.
- Most patients have concurrent interdigital or moccasin tinea pedis, and some may also have tinea cruris.
- Most patients tell about nail discomfort, especially when cutting, and many may experience pain during activities such as running and jogging.
Differential diagnosis of Tinea unguium:
- The clinical signs of tinea unguium are often difficult to distinguish from those of a number of other infectious causes of nail damage, such as Candida, mould or bacterial infection.
- Unlike dermatophytosis, candidosis of the nailsusually initiates in the proximal nail plate, and nail fold infection (paronychia) is also present.
- Bacterial infection, particularly when due to Pseudomonas aeruginosa, tends to result in green or black discoloration of nails.
- Sometimes bacterial infection can coexist with fungal infection and may require treatment in its own right.
- Many other non-infectious conditions can produce nail changes that mimic onychomycosis, but the nail surface does not usually become soft and friable as in a fungal infection.
- Non-fungal causes of nail dystrophies include onychogryphosis, psoriasis, chronic eczema and lichen planus.
Lab diagnosis of Tinea unguium
- Microscopy:
- The clinical diagnosis of fungal infection is confirmed by direct microscopic examination.
- It is sometimes possible to distinguish Cundidu infection, or infection due to moulds such as Scopuluriopsis brevicuulis from tinea unguium.
- Culture:
- Isolation of the aetiological agent in culture will permit the species of dermatophyte involved to be determined.
- It is essential to inform the laboratory if nail material is suspected of being infected with non- dermatophyte moulds, so that duplicate plates with and without cycloheximide (actidione) can be inoculated.
- The results of culture can be positive even if microscopic examination is negative, but it is more common for microscopic examination to be positive while culture is negative.
Treatment of Tinea unguium:
- Tinea unguium is a tough condition to treat.
- In general, onychomycosis should be treated with an oral anti- fungal agent.
- However, localized distal nail disease can sometimes be treated with topical antifungals such as amorolfine, ciclopirox, or tioconazole solutions.
- Topical: amorolfine should be taken at weekly intervals or tioconazole, twice daily for 6 months for fingernails and 9–12 months in case of toenails.
- Oral: itraconazole 2 or 3 pulse treatment 400 mg/day for 1 week in 4, or continuous 200 mg/day for 3 months.
- Oral griseofulvin applied for 4–8 months.
- Oral terbinafine should be taken 250 mg/day for 6–12 weeks for fingernails, 12 weeks or longer for toenails.
- Oral fluconazole 150–450 mg once weekly for 6–9 months in toenail infections, 3 months for fingernails.
- Ciclopirox solution must be applied once daily for at least 6 months.
- Response rates are low compared with oral agents used in nail infections, and topical agents are usually reserved for infections of limited extent or where they can be combined with nail removal.
- Two new oral antifungal agents, terbinafine and itraconazole, are effective in onychomycosis and have been approved for use in adults with this indication.
- Cure rates with these agents approach 80% in most trials.
- The allylamine terbinafine is now the treatment of choice for patients with dermatophytosis of the finger- nails or toenails.
- Treatment with oral terbinafine will also clear associated cutaneous lesions without additional topical treatment.
- Terbinafine has proved to be effective in HIV-infected individuals and no interactions or significant adverse effects related to the drug have been reported.
- Itraconazole is other effective alternative for dermatophyte nail infection.
- This drug persists in nail for at least 6 months and pulsed treatment (in which 1week of treatment is alternated with 3 weeks without treatment) has given encouraging results.
- Fluconazole has proven to be less effective than terbinafine or itraconazole for onychomycosis.
- With griseofulvin, up to 90% of fingernail infections can be cured in 4-8 months, but its low cure rate of 20-40% in toenail infections means that it is now less appropriate than terbinafine or itraconazole.
- The application of 40% urea ointment to the nail under occlusion for 4-7 days allows the nail to be excised after this treatment.
Prevention:
- Many individuals with onychomycosis are unaware of their fungal infection and some believe that dystrophic nails are simply part of the ageing process.
- Patients should be made aware that the disease is contagious, and can be spread to those around them.
- Individuals with untreated or partially treated plantar or interdigital tinea pedis should be informed of the risk of developing onychomycosis.
- Measures that can help to control nail infection or prevent reinfection include:
- application of antifungal powders to the feet after bathing
- wearing of absorbent cotton socks
- frequent changing of socks
- application of antifungal powders to footwear
- avoidance of occlusive footwear that increases sweating
- and wearing of protective footwear in hotels, changing rooms, gymnasiums and other public facilities.
- It is also important to keep the nails as short as possible and to avoid sharing nail clippers with other household members.