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1

What is Onychomycosis? (also known as Tinea Unguium)

Fungal Disease that can affect one or more of the anatomical components of the toenails or fingernails.

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Dermatophytes

Fungal Pathogens that invade and break down the normal keratin of the skin, hair and nails.

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Three fungal species of Onychomycosis

Dermatophytes, Yeasts, and Nondermatophyte molds

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Two most common Dermatophytes

T. rubrum and T. Mentagrophytes

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Nail Dystrophy

Characterized by thickening, scaling, and discoloration of the nail and nail bed.

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Keratin

Family of durable protein polymers that are found in epethelial cells. They provide structure strength to skin, nails, and hair.

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Candida Albicans

the fungus that causes onychomycosis in the majority of cases caused by yeast

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Non-Dermatophyte Molds

most frequently seen among elderly and the immuncompromised. Most common is Scopulariopsis, Acremonium and Fusarium.

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Hyponychium

Thickened layer of the epidermis beneath the free end of the nail

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Nail Unit

made up of the proximal nail fold (PNF), the nail matrix, the nail bed, and the hyponychium.

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Lunula

crescent shaped area visible at the base of the fingernails, active area of nail bed growth

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Eponychium

Horny structure from which the nail develops

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Nail Plate Growth

Toenail growth is slower than fingernail growth.
-fingernails grow appox 1/8inch per month - 6mths for complete
-toenail grow aprox 1/16 inch per month-* 12-18 months for complete

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Types of Onychomycosis

-Distal Lateral Subungual onychomycosis
-White superficial onychomycosis
-Proximal subungual onychomycosis
-Candidal onychomycosis

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Distal Lateral Subungual Onychomycosis(DSLO)

most common type of onychomycosis. Most often caused by T. rubrum/t. mentagrophytes. Starts as infection of hyponychium and distal or lateral nail bed. Moves subungually under the nail plate from the distal/lateral nail bed into the proximal nail bed and finally upward into the nail plate.

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Signs and Symptoms of DSLO

-distal/lateral loosening of the nail from the nail bed
-yellow/brown discoloration
-hyperkeratosis(thickening and over growth.
may also progress to total dystrophic onychomycosis

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Hyperkeratosis

overgrowth of the horny layer of the epidermis(thickening of nail and overgrowth)

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Total Dystrophic Onychomycosis

Condition characterized by total destruction of the nail plate

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White Superficial Onychomycosis (WSO)

less common type of onychomycosis than DLSO. Pathogens invades through the nail plate, then moves into the nail bed and hyponychium. Most frequently caused by T. mentagrophytes.

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Signs and Symptoms of White Superficial Onychomycosis

-white dots or tiny punctures speckled across the surface of the nail, which gradually spread to involve the entire nail. Nail plate becomes white and crumbles as infection spreads.

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Proximal Subungual Onychomycosis

Rarely seen, caused primarily by T.rubrum. Invades the nail unit through the stratum corneum of the proximal nail fold. Seen frequently in patients with AIDS. May be presenting signs of AIDS.

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Signs and Symptoms of Proximal Subungual Onychomycosis

-white discoloration under the nail plate in the area of the lunula, with the nail plate remaining intact and the distal end of the nail unit appearing normal.

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Candidal Onychomycosis

Rare condition that may occur only in individuals with a chronic Candida infection of the skin and mucous membranes. Most common pathogen is Candida Albicans.

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Signs and Symptoms of Candidal Onychomycosis

-Thickening of the nail bed
-yellow-brown discoloration of the nail plate
-swelling of the proximal and lateral nail folds that result in a "drumstick" appearance of the digits.

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Mild Onychomycosis

Less than 25% of nail affected by disease

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Moderate Onychomycosis

26% to 74% of nail affected by disease

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Severe Onychomycosis

More than 75% of nail affected by disease

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Diagnosis of Onychomycosis

Clinical
-Primary Criteria is white/yellow or orange/brown
patches or streaks
-Secondary is Onycholysis, Subungual
hyperkeratosis/debris, and Nail plate thickening
Lab
-Positive microscopic evidence
-Positive Culture of dermatophyte

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Onycholysis

loosening or detachment of the nail plate from the nail bed

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Lab Evaluation

DLSO- specimen taken from Nail bed and scrapings under nail
WSO-specimen taken from the nail plate
PSO-specimen taken from the proximal nail bed

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KOH

Microscopic evaluation of a potassium hydroxide preparation of the specimen only detects the presence or absence of fungi. Cannot specify which pathogen is present. Stain may help identify presence of fungi.

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Culture

The only method of determining which genus and species of fungi is responsible for the infection.

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Periodic Acid-Schiff (PAS)

Pathologist uses a fungal stain to help identify the presence of fungi. Like KOH, does not identify the specific pathogen.

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Mycological Cure

Negative mycology lab test (negative KOH and negative Culture)

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Clinical Cure

No residual involvement of the target nail
or
a predetermined percentage (80%-100%) of the nail that is visibly free of infection

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Complete Cure

No residual clinical involvement of the target nail
and
mycological cure (negative KOH and negative Culture)

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Nail Matrix

Thickened epitheliun at the base of a fingernail or toenail from which a new nail substance develops.

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Poor Prognosis for a Cure

-subungual hyperkeratosis >2mm
->50% of the nail infected
-Lateral nail Disease
-Total Dystrophic oncyhomycosis
-Elderly or AIDs patients