What are the different forms of onychomycosis?

There are primarily six clinical forms of onychomycosis –

1. Distal lateral subungual onychomycosis (DLSO)

DLSO is the most common form of onychomycosis and is usually caused by dermatophytes. The fungus invades from the distal or lateral undersurface of the nail plate, causing hyperkeratosis, discolouration, detachment from the nail bed and streaking of the nail.4,8

2. Superficial onychomycosis (SO)

In SO the nail surface is the only part of the nail which is infected. The nail plate can be white or black and present with a wide range of discolouration; it can appear as superficial patches or groove-like marks on the nail.4,8 The most common causes of SO are the dermatophytes.

3. Endonyx onychomycosis (EO)

In EO the distal nail plate is directly penetrated by the fungal hyphae. The nail presents a length-wise split and the nail plate is discoloured.5,8 The most common causes of EO are the dermatophytes.

4. Proximal subungual onychomycosis (PSO)

PSO is caused by a wide range of fungi and can be challenging to treat. The infection usually begins from the proximal nail and nailfold, slowly extending distally.4,8

5. Mixed pattern onychomycosis (MPO)

MPO involves the occurrence of a number of disorders observed concurrently. PSO and SO regularly occur together, similarly DLSO with SO.9

6. Totally dystrophic onychomycosis (TDO)

TDO is presented at the end stage of different forms of nail plate invasions and is caused by different organisms. The nail is completely damaged and crumbles away, while the nailbed is thickened and ridged.4

It is important to recognise the different forms of onychomycosis and choose the appropriate treatment in order to resolve the infection effectively.

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