Incidence and Epidemiology of Onychomycosis in Patients Visiting a Tertiary Care Hospital in India

Onychomycosis is a chronic fungal infection of the nails. Dermatophytes are the most common etiologic agents, but yeasts and nondermatophyte molds also constitute a substantial number of cases.¹ An accumulation of debris under distorted, deformed, thickened, and discolored nails, particularly with ragged and furrowed edges, strongly suggests tinea unguium.² Candidal onychomycosis (CO) lacks gross distortion and accumulated detritus and mainly affects fingernails.³ Nondermatophytic molds cause 1.5% to 6% of cases of onychomycosis, mostly seen in toenails of elderly individuals with a history of trauma.⁴ Onychomycosis affects 5.5% of the world population⁵ and represents 20% to 40% of all onychopathies and approximately 30% of cutaneous mycotic infections.⁶

The incidence of onychomycosis ranges from 0.5% to 5% in the general population in India.⁷ The incidence is particularly high in warm humid climates such as India.⁸ Researchers have found certain habits of the population in the Indian subcontinent (eg, walking with bare feet, wearing ill-fitting shoes, nail-biting [eg, onychophagia], working with chemicals) to be contributing factors for onychomycosis.⁹ Several studies have shown that the prevalence of onychomycosis increases with age, possibly due to poor peripheral circulation, diabetes mellitus, repeated nail trauma, prolonged exposure to pathogenic fungi, suboptimal immune function, inactivity, or inability to trim the toenails and care for the feet.¹⁰ Nail infection is a cosmetic problem with serious physical and psychological morbidity and also serves as the fungal reservoir for skin infections. Besides destruction and disfigurement of the nail plate, onychomycosis can lead to self-consciousness and impairment of daily functioning.¹¹

Nail dystrophy occurs secondary to various systemic disorders or can be associated with other dermatologic conditions. Nail discoloration and other onychia should be differentiated from onychomycosis by classifying nail lesions as distal lateral subungual onychomycosis, proximal subungual onychomycosis (PSO), CO, white superficial onychomycosis (WSO), and total dystrophic onychomycosis.¹² Laboratory investigation is necessary to accurately differentiate between fungal infections and other skin diseases before starting treatment. Our hospital-based study sought to determine the incidence and epidemiology of onychomycosis with an analysis of 134 participants with clinically suspected onychomycosis. We evaluated prevalence based on age, sex, and occupation, as well as the most common pathogens.

Materials and Methods

Study Design and Participants

The study population consisted of 134 patients with clinically suspected onychomycosis who visited the dermatology department at the Veer Chandra Singh Garhwali Government Institute of Medical Sciences and Research Institute in Uttarakhand, India (October 2010 to October 2011). A thorough history was obtained and a detailed examination of the distorted nails was conducted in the microbiology laboratory. Patient history and demographic factors such as age, sex, occupation, and related history of risk factors for onychomycosis were recorded pro forma. Some of the details such as itching, family history of fungal infection, and prior cutaneous infections were recorded. Patients who were undergoing treatment with systemic or topical antifungal agents in the 4 weeks preceding the study period were excluded to rule out false-negative cases and to avoid the influence of antifungal agents on the disease course.

Assessments

Two samples were taken from each patient on different days. Participants were divided into 4 groups based on occupation: farmer, housewife, student, and other (eg, clerk, shopkeeper, painter). Clinical presentation of discoloration, onycholysis, subungual hyperkeratosis, and nail thickening affecting the distal and/or lateral nail plate was defined as distal lateral subungual onychomycosis; discoloration and onycholysis affecting the proximal part of the nail was defined as PSO; association with paronychia and distal and lateral onycholysis was defined as CO; white opaque patches on the nail surface were defined as WSO; and end-stage nail disease was defined as total dystrophic onychomycosis.

Prior to sampling, the nails were cleaned with a 70% alcohol solution. Nail clippings were obtained using presterilized nail clippers and a blunt no. 15 scalpel blade and were placed on sterilized black paper. Each nail sample was divided into 2 parts: one for direct microscopy and one for culture. Nail clippings were subjected to microscopic examination after clearing in 20% potassium hydroxide solution. The slides were examined for fungal hyphae, arthrospores, yeasts, and pseudohyphal forms. Culture was done with Emmons modification of Sabouraud dextrose agar (incubated at 27°C for molds and 37°C for yeasts) as well as with 0.4% chloramphenicol and 5% cycloheximide (incubated at 27°C). Culture tubes were examined daily for the first week and on alternate days thereafter for 4 weeks of incubation.

Dermatophytes were identified based on the colony morphology, growth rate, texture, border, and pigmentation in the obverse and reverse of culture media and microscopic examination using lactophenol cotton blue tease mount. Yeast colonies were identified microscopically with Gram stain, and species were identified by germ tube, carbohydrate assimilation, and fermentation tests.¹³ Nondermatophyte molds were identified by colony morphology, microscopic examination, and slide culture. Molds were considered as pathogens in the presence of the following criteria: (1) absence of other fungal growth in the same culture tube; (2) presence of mold growth in all 3 samples; and (3) presence of filaments identified on direct examination.