Author: Cindy Li, DO, Dermatologist and Cosmetic Surgeon, Department of Dermatology, Kaiser Permanente Medical Group
Coauthor(s): Richard K Scher, MD, Professor of Dermatology, University of North Carolina
Psoriatic nail disease has many clinical signs. Most psoriatic nail disease occurs in patients with clinically evident psoriasis; it only occurs in less than 5% of patients with no other cutaneous findings of psoriasis. An estimated 10-55% of all patients with psoriasis have psoriatic nail disease. Approximately 7 million people in the United States have psoriasis. About 150,000-260,000 new cases of psoriasis are diagnosed each year. US physicians see 1.5 million patients with psoriasis per year. Severe psoriatic nail disease can lead to functional and social impairments if left untreated.
The Medscape Psoriasis Resource Center may be of interest.
The pathogenesis of the psoriatic nail disorder is not completely known. Nail psoriasis may be due to a combination of genetic, environmental, and immune factors. A well-known fact is that a familial aggregation of psoriasis exists. Studies have linked psoriasis with certain human leukocyte antigen subtypes (eg, Cw6, B13, Bw57, Cw2, Cw11, B27). A T-cell–mediated inflammatory process is being investigated as part of the pathogenesis of psoriasis.
Psoriatic nail disease occurs in 10-55% of all patients with psoriasis. Approximately 7 million people in the United States have psoriasis. Psoriasis affects 2-3% of the US population. Less than 5% of psoriatic nail disease cases occur in patients without other cutaneous findings of psoriasis. About 10-20% of people with psoriasis also have psoriatic arthritis. Nail changes are seen in 53-86% of patients with psoriatic arthritis.
Psoriasis tends to run in families. In Farber's questionnaire study of 2100 patients,1 36% of patients reported the presence of psoriasis in at least 1 relative. Among siblings, 8% are affected if neither parent has psoriasis. This percentage increases to 16-25% if 1 parent or sibling has the disease, and it increases up to 75% if both parents are affected. If 1 twin has psoriasis, the other twin is at an increased risk of having psoriasis (25% for fraternal twins, 65% for identical twins).
Most psoriatic nail disease occurs in people with clinically evident psoriasis. The diagnosis of psoriatic nail disease without cutaneous psoriasis can be challenging because of the low index of suspicion and the lack of personal/family history of psoriasis.
The clinical findings associated with psoriatic nail disease correlate with the anatomical location of the nail unit that is affected by the disease. The nail unit is composed of the nail plate, the nail bed, the hyponychium, the nail matrix, the nail folds, the cuticle, the anchoring portion of the nail bed, and the distal phalangeal bones. The nail plate is the largest component of the nail unit. The nail matrix gives rise to the nail plate. Any defect to the matrix results in onychodystrophy of the growing nail plate. The proximal nail matrix forms the dorsal portion of the nail plate, whereas the distal matrix forms the ventral part of the nail plate. The clinical presentation may vary depending on the location and the severity of inflammation of the affected nail unit.
[ CLOSE WINDOW ]Anatomy of the nail, superior view.
- Below is a summary of the clinical signs of nail psoriasis and the portion of the nail unit that is affected followed by a definition.
- Oil drop or salmon patch/nail bed2 : This lesion is a translucent, yellow-red discoloration in the nail bed resembling a drop of oil beneath the nail plate. This patch is the most diagnostic sign of nail psoriasis.
- Pitting/proximal nail matrix: Pitting is a result of the loss of parakeratotic cells from the surface of the nail plate.
- Beau lines/proximal nail matrix: These lines are transverse lines in the nails due to intermittent inflammation causing growth arrest lines.
- Leukonychia/midmatrix disease: Leukonychia is areas of white nail plate due to foci of parakeratosis within the body of the nail plate.
- Subungual hyperkeratosis/hyponychium: Subungual hyperkeratosis affects the nail bed and the hyponychium. Excessive proliferation of the nail bed can lead to onycholysis.
- Onycholysis/nail bed and nail hyponychium: Onycholysis is a white area of the nail plate due to a functional separation of the nail plate from its underlying attachment to the nail bed. It usually starts distally and progresses proximally, causing a traumatic uplifting of the distal nail plate. Secondary microbial colonization may occur.
- Nail plate crumbling/nail bed or nail matrix: Nail plate weakening due to disease of the underlying structures causes this condition.
- Splinter hemorrhage/dilated tortuous capillaries in the dermal papillae: Splinter hemorrhages are longitudinal black lines due to minute foci of capillary hemorrhage between the nail bed and the nail plate. This is analogous to the Auspitz sign of cutaneous psoriasis, which is the pinpoint bleeding seen beneath the psoriatic plaques.
- Spotted lunula/distal matrix: This is an erythematous patch of the lunula.
- Psoriatic arthritis with nail changes/phalanx
- Psoriatic nail disease can also occur with onychomycosis and paronychia.
- Most people with psoriatic arthritis have nail changes that can be classified as follows:
- Type I - Classic distal interphalangeal joint involvement (5% of patients)
- Type II - Arthritis mutilans
- Type III - Symmetric polyarthritis
- Type IV - Asymmetric oligoarthritis (the most common type of psoriatic arthritis, occurring in 70% of patients)
- Type V - Ankylosing spondylitis
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Psoriatic nail disease may be due to a combination of genetic, environmental, and immune factors. A well-known fact is that a familial aggregation of psoriasis exists. Recent studies have linked psoriasis with certain human leukocyte antigen subtypes (eg, Cw6, B13, Bw57, Cw2, Cw11, B27). A T-cell–mediated inflammatory processing is being investigated as part of the pathogenesis of psoriasis.