Psoriatic Nails

Psoriatic Nails (Also Discussed in Chapter 22: Diseases and Abnormalities of Nails)

Involvement of nails is very common in patients with psoriasis (also discussed in Chapter 22: Diseases and Abnormalities of Nails). It is often mistaken for, and treated incorrectly as, a nail fungus infection (onychomycosis).
Psoriatic nail dystrophy is a chronic, primarily cosmetic condition; however, in some instances, thickened psoriatic toenails can become painful, and psoriatic fingernail deformities may be embarrassing and interfere with function.
Severe nail dystrophy is more commonly noted in patients who have psoriatic arthritis.

Pitting is the most characteristic nail finding in psoriasis. Pitting presents as tiny punctate depressions on the nail plate and arises from psoriasis in the nail matrix (nail root) (Fig. 14.24).
Onycholysis represents a separation of the nail plate from the underlying pink nail bed. The separated portion is white or yellow-white and opaque, in contrast to the pink translucence of the attached portion (Fig. 14.25).
“Oil spots”/“oil drops” are orange-brown colorations that appear under the nail plate. They are the result of psoriasis of the nail bed (Fig. 14.26).
Thickening, or subungual hyperkeratosis, refers to a buildup of scale beneath the nail plate. It resembles onychomycosis, with which it is often confused and may coexist, particularly in toenails (Fig. 14.27).

Differential Diagnosis

Onychomycosis

Eczematous Dermatitis with Secondary Nail Dystrophy

Lacks subungual hyperkeratosis. Eczema is noted in the area of the proximal nail fold.

Management

Treatment is challenging and generally unrewarding, but measures listed below may be helpful.
Careful trimming and paring of the nails.
A superpotent (class 1, e.g., clobetasol 0.05% ointment) topical steroid applied daily to the proximal nail folds, followed by covering with a plastic wrap or glove. Alternatively Cordran tape may be used.
Taclonex ointment (combination of topical steroid and vitamin D analog) applied daily to the proximal nail fold with or without occlusion.
Tazarotene (Tazorac) 0.1% gel applied daily to the proximal nail fold.
Intralesional corticosteroids injected into the nail matrix every 4 to 6 weeks. The proximal and/or lateral nail fold is first sprayed with a refrigerant spray (e.g., Gebauer's ethyl chloride) for anesthesia, and 2.5 mg/mL is injected with a 30-gauge needle.
At present, the systemic medications most commonly used to treat nail psoriasis are methotrexate, retinoids, and cyclosporine. All have potential serious side effects and toxicities, and, in most cases, the psoriatic nail disease recurs after the systemic therapy is stopped.
The biologics (e.g., infliximab, adalimumab, etanercept) are often used for intractable cases, particularly when psoriatic arthritis is also present.