Fungal nail infection (onychomycosis) Definition ,Causes and Treatment

Definition
Onychomycosis is infection of the nails of the fingers or toes caused by dermatophytes (fungi that live on the outer keratinous layer of the skin), yeasts or
moulds.


Causes
90% of toenail and 50% of fingernail infections are caused by the same Trichophyton and Epidermophyton species that cause athlete’s foot.
Predisposing factors include: increasing age, male gender, diabetes, nail trauma,
excessive sweating, peripheral vascular disease, poor hygiene, athlete’s foot,
immunodeficiency and chronic exposure of the nails to water


Signs and symptoms
- The nail is thickened and has turned yellow or white.
- Changes usually start at the top of the nail but may spread across to the sides and down towards the nail base.
- Debris created as a result of the infection accumulates under the nail.
- There is scaling and distortion of the nail.
- The nail may become brittle and some or all of it may break off.


Treatment
Onychomycosis is one of the most difficult fungal infections to treat because of the time it takes for the nail to grow, the hardness of the nail plate and location
of the infectious process (between the nail bed and plate).

Prescription treatments
Oral therapies. Terbinafine and itraconazole are considered the systemic treatments of choice.
Tioconazole 28% cutaneous solution is licensed for topical treatment 
of onychomycosis, but there is little clinical evidence of its effectiveness.

Non-prescription treatment
amorolfine 5% nail lacquer Amorolfine 5% nail lacquer is licensed for pharmacy sale for the treatment of mild cases of DLSO, affecting up to two nails, in patients aged 18 years or over.

- Amorolfine is a morpholine derivative, used topically as an antifungal, with a broad spectrum of activity against dermatophytes, other fungi and yeasts.

Amorolfine  mechanism:
- Its fungicidal action is based on ergosterol depletion and the accumulation of
ignosterol in fungal cytoplasmic membrane, which causes the fungal cell wall
to thicken and chitin to be deposited.

- The nail lacquer formulation builds a non-water-soluble film on the nail plate that remains at the application site for a week, acting as a depot for the drug.
- The product must be used weekly for up to 9 months, until all the infected nail
has grown out and been replaced by healthy nail tissue.

Adverse effects are rare and minor, amorolfine is not systematically absorbed
and there are no known interactions with other drugs.