Multiple nails

Clinical features

A fungal infection of the nail, referred to as “onychomycosis” or “tinea unguium,” is an infection of the nail in which the organism changes the structure and shape of the nail plate, leading to thickening, changes in appearance, and/or discoloration. Changes in appearance are dependent on the organism and site of infection.

• There are five common types of onychomycosis.

  • Distal dystrophic onychomycosis (distal subungual onychomycosis) is the most common type. It is caused by Trichophyton rubum, which infects the distal nail unit, causing distal nail plate separation and subungual hyperkeratosis.

  • White superficial onychomycosis is commonly caused by T. mentagrophytes, which grow on the surface of the nail plate and lead to further destruction of the nail plate if left untreated.

  • Proximal subungual onychomycosis, which may also be caused by T. rubum, is the least common type and is associated with the organism entering through the disruption of the cuticle region. This type often causes nail loss and is associated with patients with untreated HIV.

  • Candida onychomycosis involves a yeast infection along the proximal or lateral nail folds, with the most common type involving the hands. It is associated with patients who have increased water exposure to their hands.

  • Total dystrophic onychomycosis is when the disease completely absorbs the nail plate and can lead to permanent damage, even after successful treatment.

Differential diagnosis

The differential for onychomycosis includes inflammatory nail dystrophy, bacterial nail infections, traumatic onychodystrophy, nail bed or osseous tumors, yellow nail syndrome, malignancies of the nail unit, and uncommon nail conditions like idiopathic onycholysis. Similar symptoms can sometimes also result from the use of certain drugs.

• Inflammatory nail dystrophy is the result of an inflammation of the nail unit, which includes the matrix and nail bed. These changes are associated with the location and degree of inflammation; common types are psoriatic nail dystrophy, lichen planus (LP) nail involvement, and contact dermatitis.

  • Psoriatic nail dystrophy is associated with the so-called “pitting” and classic “oil stain” signs; pain is associated with nail bed inflammation.

  • LP nail involvement is associated with nail plate splitting that has a winglike or so-called “pterygium” appearance ( Fig. 16.1 ).

    

  • Contact dermatitis results from the inflammation of the nail folds after exposure to a sensitizing agent, such as acrylics (false nails) or topical nail preparations; if chronic exposure to the agent occurs, it can cause nail changes.

• Bacterial nail infections present with the causative organism usually infiltrating the borders of the nail unit and are associated with nail plate discoloration.

• Traumatic onychodystrophy results from injury of the nail unit; trauma can include direct traumatic injury or accumulation of repetitive microtrauma. Black-purple discoloration is common when there is a subungual hemorrhage.

• Nail bed or osseous tumors can cause structural changes to the nail unit, resulting in nail plate deformities.

• Yellow nail syndrome is a rare condition that results from increased lymphatic effusion, causing yellowing of the nail plate.

• Malignancies of the nail unit can cause structural changes, resulting in nail plate deformities. Black discoloration or a streak on the nail plate and/or unit may be an indicator of malignant melanoma.

• Uncommon nail conditions resembling onychomycosis include drug-induced nail dystrophy, pachyonychia congenita, and idiopathic onycholysis.

• Some drugs cause onycholysis (lifting of the nail plate from the nail bed) or photo-onycholysis via damage to the nail bed. The list of drugs known to cause these reactions includes psoralens, doxycycline, oral contraceptives, diuretics (thiazides), antibiotics (fluoroquinolone), nonsteroidal antiinflammatory drugs (NSAIDs), taxanes, captopril, retinoids, phenothiazines, clofazimine, and some anticonvulsants (sodium valproate).

Work-up

Onychomycosis requires disease confirmation by way of laboratory diagnosis because of the varying treatment options and differing lengths of therapies. Topical agents may require up to a year of therapy. Meanwhile, oral agents tend to be safe but can have various medical contraindications and potential drug interactions.

• Scraping subungual debris and placing it on a glass slide, staining it with potassium hydroxide (KOH), and then heating the slide results in an easy-to-perform slide preparation that can be examined in the clinic under a microscope to identify hyphae and quickly confirm the diagnosis.

• Diagnosis can be confirmed by culturing the nail plate and subungual debris. Culturing, unfortunately, is time consuming, often yields false-negative results, and may produce contaminants, all of which can delay therapy. Use of a dermatophyte test medium (DTM) provides results much more quickly, but the results are generalized; fortunately, most agents treat dermatophytes very well. A final diagnostic method is histologic examination; periodic acid–Schiff (PAS) staining can confirm hyphae involvement, rule out contamination, and assist in ruling out inflammatory, nonmycotic nails.

Initial steps in management

Treatment options vary; the two most common methods involve topical agents and oral antifungal medications. A decision on treatment course is determined by the patient’s medical history, drug interactions, and patient compliance with the recommended course of treatment. Topical treatments are lengthy and less successful; oral medications have shorter therapeutic courses and higher success rates but carry a higher risk for an adverse medical outcome.