Onychomycosis: causes, symptoms, diagnosis, and treatment

Onychomycosis is a nail infection caused by dermatophytes, yeasts, and non-dermatophyte filamentous fungi. Onychomycosis caused solely by dermatophytes is also known as tinea unguium. Toenail ringworm is mostly transmitted from tinea pedis, while fingernail ringworm may be transmitted from tinea manuum or by direct contact with ringworm on other areas of the body.


Onychomycosis is often caused by trichophyton rubrum, trichophyton mentagrophytes, and epidermophytom floccosum. Other pathogens are trichophyton schoenleinii, trichophyton violaceum, trichophyton tonsurans, trichophyton rosaceum, and trichophyton concentricum. However, microsporum gypseum, microsporum canis, microsporum ferrugineum, and microsporum audouinii are less likely to cause onychomycosis.

Onychomycosis can also be caused by other filamentous fungi, yeast-like fungi, and yeasts. Occasionally, it can also be caused by cladosporium, fusarium, and aspergillus terreus, which are mostly found in malnourished nails. It is determined that candida albicans, scopulariopsis brevicaulis, aspergillus flavus, aspergillus fumigatus, aspergillus niveoglaucus, aspergillus sydowii, aspergillus ustus, aspergillus versicolor, cladosporium, fusarium, and scopulariopsis brevicaulis can cause infections. In addition to candida albicans, candida parapsilosis often causes onychomycosis.

Signs and Symptoms

Superficial white onychomycosis (SWO)

Pathogens invade the surface of nail plates and survive in the superficial nail plates. White, opaque, sharply demarcated spots, or soft, fragile transverse furrows occur on the nail plates, gradually extending and fusing, developing into yellowish white lesions.

Figure 1 superficial white onychomycosis

Distal and lateral subungual onychomycosis (DLSO)

This illness is the most common. The pathogens infect the stratum corneum of the distal and lateral nails, and then extend to the nail beds. The nail plate is initially normal. Subsequently, the expansion of inflammation causes subungual keratinocyte proliferation, and the nail plate is freed and raised, eventually the nail plate is separated from the nail bed. With the development of the illness, pathogens eventually invade the nail plate, and the nail plate is dirty, with changed color and solidity, with increased brittleness, with motheaten lesions. The progress of the illness varies with individual differences, and a long duration is generally present.

Figure 2 distal and lateral subungual onychomycosis

Figure 3 distal and lateral subungual onychomycosis

Proximal subungual onychomycosis (PSO)

Pathogens invade the stratum corneum of the proximal nail cuticles initially. The clinical manifestations are white spots, initially localized to the lunula of nails, gradually extending outwards as the nail plate grows or extending spontaneously. The illness is often accompanied by paronychia.

Figure 4 proximal subungual onychomycosis

Endonyx onychomycosis (EO)

This illness is less common. The lesions are localized to the nail plate, and subungual areas are not involved. The nail plate lesion is white or grayish white, without significant thickening or atrophy, without obvious inflammation.

Figure 5 endonyx onychomycosis

Total dystrophic onychomycosis (TDO)

If onychomycosis aggravates and involves the entire nail plate, the entire nail plate may be eroded, damaged, and dropped off, or the nail bed may be abnormally thickened.

Figure 6 total dystrophic onychomycosis

Candidal onychia and paronychia

The illness is manifested by chronic inflammation of the proximal and lateral nail folds. Onycholysis and nail thickening may be present but less common. The inflammation of nail folds is manifested by dark red, mild, chronic swelling, usually without suppuration. All nails can be involved in patients with chronic mucocutaneous candidiasis. with thickened nail plates, thrush, and skin lesions.

In addition, mixed pattern onychomycosis (MPO) and secondary onychomycosis can occur.


According to clinical manifestations, positive fungal microscopy, and fungal hyphae or spores found in histopathological examinations, the disease can be diagnosed. Potassium hydroxide (KOH) microscopic examination can assist in the diagnosis.


Topical treatment

Topical medications include 5% amorolfine nail polish, 8% ciclopirox cream, 30% glacial acetic acid, 12% lactic acid, 95% alcohol solution, 10% iodine tincture, 40% urea cream, and compound salicylic acid ointment.

Laser treatment, photodynamic therapy, and iontophoresis can be considered

Systemic treatment

Systemic medications are terbinafine, itraconazole, fluconazole, and efinaconazole.