Elderly individuals predisposed to tinea unguium
A 10-year retrospective study at Singapore General Hospital (SGH) has shown that majority of patients with tinea unguium, a common nail infection, are aged ≥60 years. In this cohort, patients of Indian and other ethnicities are over-represented for tinea unguium compared to Chinese and Malay patients.
Additionally, the most common dermatophyte isolated is Trychophyton (T.) rubrum, while T. verrucosum, T. violaceum and T. soudanense are rare.
“With the increasingly ageing population worldwide, tinea unguium should be expected to become an emerging health problem, as older people are more prone to the infection,” researchers said.
Results of fungal nail cultures were retrieved from the microbiology department of SGH. Researchers inoculated samples from nail scrapings and clippings onto agar plates (Sabouraud dextrose agar with chloramphenicol and Mycosel agar). Included in the analyses were specimens that grew dermatophytes.
Dermatophytes grew from a total of 229 (male: n=164; 71.6 percent; female: n=65; 28.4 percent; mean patient age 58 years) nail specimens. Specimens mostly came from patients aged >50 years (n=162; 70.7 percent) and 60–79 years (n=100; 43.7 percent). [Singapore Med J 2018;59:524-527]
In term of ethnicity, specimens were isolated from Chinese patients (n=160; 69.9 percent), Indian patients (n=36; 15.7 percent), Malay patients (n=18; 7.9 percent) and from those of other ethnicities (n=15; 6.6 percent).
“The ethnic make-up of our patients with tinea unguium caused by dermatophytes was different from that of the general Singapore population, which was 75.3 percent Chinese, 13.8 percent Malay, 8.6 percent Indian and 2.3 percent other ethnicities in 2006,” researchers said. [https://www.singstat.gov.sg/media/files/publications/population/population2016.pdf]
In this cohort, Indian patients and those of other ethnicities were over-represented, while Chinese and Malay patients were under-represented (p=0.001).
The following dermatophytes were isolated: T. rubrum (n=93; 40.6 percent), T. mentagrophytes (n=60; 26.2 percent), unidentified T. spp. (n=57; 24.9 percent), T. tonsurans (n=10; 4.4 percent), Epidermophyton floccosum (n=5; 2.2 percent), T. verrucosum (n=2; 0.9 percent), T. soudanense (n=1; 0.4 percent) and T. violaceum (n=1; 0.4 percent).
According to researchers, it is seldom for children to develop tinea unguium because their nails grow faster than adults’, which reduces the odds of dermatophytes invading their nail plates. Nails grow at a slower rate when people age, thus making it likely for nail plates to be invaded by dermatophytes.
“The nails of elderly people may also be subject to minor trauma due to poor eyesight, impaired mobility and poor nail care. Such dystrophic nails may be prone to invasion by dermatophytes, and even onycholysis and onychogryphosis,” they said.
Peripheral vascular diseases and diabetes mellitus, both of which are common comorbidities among elderly people, are additional factors that predispose patients to tinea unguium, they added.
“Tinea unguium affects not only the cosmetic appearance of nails but also the patient’s dexterity. It serves as a portal of entry for bacterial infection into the patient’s skin and may even aid in spreading the dermatophyte infection to the skin and nails of other people in the community,” researchers said.