Epidemiology of onychomycoses assessed by histomycology in psoriatic patients

Global prevalence of onychomycosis in general and special populations: An updated perspective

BACKGROUND

Onychomycosis is a chronic nail disorder commonly seen by healthcare providers; toenail involvement in particular presents a treatment challenge.

OBJECTIVE

To provide an updated estimate on the prevalence of toenail onychomycosis.

METHODS

We conducted a literature search using PubMed, Embase and Web of Science. Studies reporting mycology-confirmed diagnoses were included and stratified into (a) populations-based studies, and studies that included (b) clinically un-suspected and (c) clinically suspected patients.

RESULTS

A total of 108 studies were included. Based on studies that examined clinically un-suspected patients (i.e., with or without clinical features suggestive of onychomycosis), the pooled prevalence rate of toenail onychomycosis caused by dermatophytes was 4% (95% CI: 3-5) among the general population; special populations with a heightened risk include knee osteoarthritis patients (RR: 14.6 [95% CI: 13.0-16.5]), chronic venous disease patients (RR: 5.6 [95% CI: 3.7-8.1]), renal transplant patients (RR: 4.7 [95% CI: 3.3-6.5]), geriatric patients (RR: 4.7 [95% CI: 4.4-4.9]), HIV-positive patients (RR: 3.7 [95% CI: 2.9-4.7]), lupus erythematosus patients (RR: 3.1 [95% CI: 1.2-6.3]), diabetic patients (RR: 2.8 [95% CI: 2.4-3.3]) and hemodialysis patients (RR: 2.8 [95% CI: 1.9-4.0]). The prevalence of onychomycosis in clinically suspected patients was significantly higher likely due to sampling bias. A high degree of variability was found in a limited number of population-based studies indicating that certain pockets of the population may be more predisposed to onychomycosis. The diagnosis of non-dermatophyte mould onychomycosis requires repeat sampling to rule out contaminants or commensal organisms; a significant difference was found between studies that performed single sampling versus repeat sampling. The advent of PCR diagnosis results in improved detection rates for dermatophytes compared to culture.

CONCLUSION

Onychomycosis is an underrecognized healthcare burden. Further population-based studies using standardized PCR methods are warranted.

Overall Prevalence and Prevalence Compared among Psoriasis Treatments of Onychomycosis in Patients with Nail Psoriasis and Fungal Involvement

BACKGROUND

Whether nail psoriasis can increase the risk of onychomycosis is still being debated, and data relating to the prevalence of onychomycosis among psoriasis patients receiving different treatments is limited.

OBJECTIVES

To investigate the overall prevalence and prevalence compared among psoriasis treatments of onychomycosis in patients with nail psoriasis and fungal involvement.

METHODS

A prospective study of three groups of nail psoriasis being treated with only topical medication, methotrexate, or biologics (25 patients per group, 150 nails) was conducted at Siriraj Hospital (Bangkok, Thailand) during November 2018 to September 2020. Demographic data, psoriasis severity, and nail psoriasis severity were recorded. The nail most severely affected with psoriasis on each hand was selected for mycological testing. Potassium hydroxide, periodic acid-Schiff stain, and fungal culture were performed.

RESULTS

The prevalence of onychomycosis in nail psoriasis was 35.3%. Among the treatment groups, the prevalence of onychomycosis was significantly higher in the methotrexate group than in the topical treatment and biologic treatment groups (p = 0.014). Candida spp. was the main causative organism, followed by Trichophyton rubrum. Thumb was most commonly affected (59.3%). The most common abnormality of the nail matrix and the nail bed was pitted nail (71.3%) and onycholysis (91.3%), respectively. Multivariate analysis revealed diabetes, wet-work exposure, and methotrexate treatment to be predictors of onychomycosis.

CONCLUSIONS

Several factors, including psoriasis treatment, were shown to increase the risk of onychomycosis in nail psoriasis. Further research is needed to determine whether biologic agents, especially interleukin-17 inhibitors, can increase risk of onychomycosis and Candida infection/colonization of the nails.

The prevalence of culture-confirmed toenail onychomycosis in at-risk patient populations

Onychomycosis is a fungal infection of the nail and is the most common nail affliction in the general population. Certain patient populations are at greater risk of infection and the prevalence of onychomycosis reported in the literature has yet to be summarized across these at-risk groups. We performed a systematic review of the literature and calculated pooled prevalence estimates of onychomycosis in at-risk patient populations. The prevalence of dermatophyte toenail onychomycosis was as follows: general population 3.22% (3.07, 3.38), children 0.14% (0.11, 0.18), the elderly 10.28% (8.63, 12.18), diabetic patients 8.75% (7.48, 10.21), psoriatic patients 10.22% (8.61, 12.09), HIV positive patients 10.40% (8.02, 13.38), dialysis patients 11.93% (7.11, 19.35) and renal transplant patients 5.17% (1.77, 14.14). Dialysis patients had the highest prevalence of onychomycosis caused by dermatophytes, elderly individuals had the highest prevalence of onychomycosis caused by yeasts (6.07%; 95% CI = 3.58, 10.11) and psoriatic patients had the highest prevalence of onychomycosis caused by non-dermatophyte moulds (2.49%; 95% CI = 1.74, 3.55). An increased prevalence of onychomycosis in certain patient populations may be attributed to impaired immunity, reduced peripheral circulation and alterations to the nail plate which render these patients more susceptible to infection.

Comparison of diagnostic methods in the evaluation of onychomycosis

Onychomycosis is a common nail problem, accounting for up to half of all nail diseases. Several nail disorders may mimic the onychomycosis clinically. Therefore, a sensitive, quick, and inexpensive test is essential for screening nail specimens for the administration of the proper drug. The aim of this study was to compare 4 different diagnostic methods in the evaluation of onychomycosis and to determine their sensitivity, specificity, positive predictive value, and negative predictive value. In a cross-sectional study, nail specimens were collected from 101 patients suspected to have onychomycosis during a 14-month period. The nail specimens were examined using potassium hydroxide (KOH) 20 %, KOH-treated nail clipping stained with periodic acid-Schiff (KONCPA), and calcofluor white (CFW) stain, and grew a fungal culture. The culture was chosen as the gold standard for statistical analysis using the McNemar and chi-square tests. Out of 101 patients, 100 (99 %) patients had at least 1 of the 4 diagnostic methods positive for the presence of organisms. The positive rates for the fungal culture, KOH preparation, CFW, and KONCPA were 74.2, 85.1, 91.09, and 99.01 %, respectively. The sensitivity and negative predictive value of KONCPA was 100 %. KONCPA was the most sensitive among the tests and was also superior to other methods in its negative predictive value. KONCPA was easy to perform, rapid, and gave significantly higher rates of detection of onychomycosis compared to the standard methods of KOH preparation and fungal culture. Therefore, KONCPA should be the single method of choice for the evaluation of onychomycosis.

Clinicopathologic presentations of dermatomycoses in cancer patients

Many of the skin fungal infections in cancer patients may look similar to those infections in non-cancer patients. However, in some cases, they become more extensive and even life threatening. Prolonged and severe neutropenia is the main risk factor for the dramatic issue of fungal infections. The dermatomycoses in cancer patients can be classified in four broad groups: primary superficial dermatophytoses, primary superficial yeast infections, opportunistic mold infections with distinct potential for dissemination and secondary cutaneous manifestations of fungaemia. Occasionally, more than one fungus are found inside a given skin lesion. A special condition is represented by the mycotic colonization of mucosal squamous cell carcinomas. Angio-invasion by fungi accounts for the frequency of disseminated infections prevailing in immunocompromised cancer patients. In case of skin involvement, the dermatologist may assist by recognizing subtle semiological signs and performing biopsies for swift histological examination, molecular biology and/or culture.

Emerging therapeutic agents for onychomycosis

Onychomycosis is a frequent disorder that represents the most prevalent fungal infection, particularly among older individuals. Diverse fungi of the dermatophyte, non-dermatophyte mold and yeast families have been reported to be responsible for onychomycosis. The output from the pharmaceutical industry of new antifungals to treat onychomycosis has been limited over the last decade. Present treatment options include both oral and topical drugs, with oral therapies giving better outcomes. However, neither of these treatment options provides high cure rates that are durable. At present, azoles and allylamines are keeping the pivotal roles. New derivatives with a favorable risk-benefit ratio and new formulations of older azoles seem to be promising. Thus, ongoing drug development activities have focused on novel delivery technologies to facilitate incorporation of existing antifungal drugs inside the nail plate and the discovery of new active antifungals.