Deformities are often considered together with dystrophies, but the two are slightly different; deformities are generally considered to be gross changes in nail shape, whereas dystrophies are changes in nail texture or composition (eg, onychomycosis).
About 50% of nail dystrophies result from fungal infection. The remainder result from various causes, including trauma, congenital abnormalities, psoriasis, lichen planus, and occasionally cancer. Diagnosis may be obvious on examination, but often fungal scrapings and culture are done. Dystrophies may resolve with treatment of the cause, but if not, manicurists may be able to hide nail changes with appropriate trimming and polishes.
In some congenital ectodermal dysplasias, patients have no nails (anonychia). In pachyonychia congenita, the nail beds are thickened, discolored, and transversely hypercurved (pincer nail deformity). Nail-patella syndrome (see Nail-Patella Syndrome) causes triangular lunulae and partially absent thumb nails. Patients with Darier disease can have nails with red and white streaks and a distal V-shaped nick.
Deformities and dystrophies associated with systemic problems:
In Plummer-Vinson syndrome (esophageal webs caused by severe, untreated iron deficiency), 50% of patients have koilonychia (concave, spoon-shaped nails).
Yellow nail syndrome (characterized by hard, hypercurved, transversely thickened, yellow nails) occurs in patients with lymphedema of limbs, pleural effusion, and (usually) ascites.
Half-and-half nails occur with renal failure; the proximal half of the nail is white, and the distal half is pink or pigmented.
White nails occur with cirrhosis, although the distal third may remain pinker.
Beau lines are horizontal grooves in the nail plate that occur when nail growth temporarily slows, which can occur after infection, trauma, or systemic illness. Onychomadesis similarly results from temporary growth arrest of the nail plate and differs from Beau lines in that the full thickness of the nail is involved, causing a proximal separation of the nail plate from the nail bed. It most frequently occurs several months after hand-foot-and-mouth disease but can occur after other viral infections. Nails affected by Beau lines or onychomadesis regrow normally with time.
Deformities associated with dermatologic conditions:
In psoriasis, nails may have a number of changes, including irregular pits, oil spots (localized areas of tan-brown discoloration), separation of part of the nail from the nail bed (onycholysis), and thickening and crumbling of the nail plate.
Lichen planus of the nail matrix causes scarring with early longitudinal ridging and splitting of the nail and later leads to pterygium formation.
Pterygium of the nail is characterized by scarring from the proximal nail outward in a V formation, which leads ultimately to loss of the nail.
Alopecia areata can be accompanied by regular pits that form a pattern.
Topical tacrolimus 0.1% and intralesional corticosteroid injections may help treat nail deformities associated with psoriasis and lichen planus.
Cancer chemotherapy drugs (especially the taxanes) can cause melanonychia (nail plate pigmentation), which can be diffuse or may occur in transverse bands. Some drugs can cause characteristic changes in nail coloration:
Tobacco smoking can result in yellow or brownish discoloration of nails and fingertips.
White transverse lines of the nails (Mees lines) may occur with chemotherapy, acute arsenic intoxication, malignant tumors, MI, thallium and antimony intoxication, fluorosis, and even during etretinate therapy. They also develop with trauma to the finger, although traumatic white lines usually do not span the entire nail. The fungus Trichophyton mentagrophytes causes a chalky white discoloration of the nail plate.
Green-nail syndrome is caused by infection with Pseudomonas. It is generally a harmless infection, usually of 1 or 2 nails, and is noteworthy for its striking blue-green color. It often occurs in patients with onycholysis or chronic paronychia whose nails have been immersed in fresh water for a long period. Treatment is most effective with soaks of 1% acetic acid solution or alcohol diluted 1:4 with water. Patients should soak their affected nails twice a day for 10 min and should avoid trauma and excess moisture. Frequent clipping of the nail increases the response to treatment.
Median nail dystrophy:
Median nail dystrophy (median canaliform dystrophy) is characterized by small cracks in the nail that extend laterally and look like the branches of an evergreen tree (eg, fir tree, such as a Christmas tree). The cracks and ridges are similar to those seen in habit-tic nail deformity (which is dystrophy of the central nail caused by repetitive trauma to the nail matrix resulting from rubbing or picking with another finger). The cause is unknown in some cases, but trauma is thought to play a role. Frequent use of personal digital devices that subject the nails to repetitive striking has been implicated in several cases. Tacrolimus 0.1% at bedtime without occlusion has been successful when patients stop all activities that might lead to repetitive low-level trauma.
Melonychia striata are hyperpigmented bands that are longitudinal and extend from the proximal nail fold and cuticle to the free distal end of the nail plate. In dark-skinned people, these bands may be a normal physiologic variant requiring no treatment. Other causes include trauma, pregnancy, Addison disease, post-inflammatory hyperpigmentation, and the use of certain drugs, including doxorubicin, 5-fluorouracil, zidovudine (AZT), and psoralens. Hyperpigmented bands can also occur in benign melanocytic nevi and malignant melanoma. Hutchinson sign (extension of hyperpigmentation through the lunula and cuticle and into the proximal nail fold) may signal a melanoma in the nail matrix. Rapid biopsy and treatment are essential.
Onychogryphosis is a nail dystrophy in which the nail, most often on the big toe, becomes thickened and curved. It may be caused by ill-fitting shoes. It is common among the elderly. Treatment consists of trimming the deformed nails.
Onycholysis is separation of the nail plate from the nail bed or complete nail plate loss. It can occur as a drug reaction in patients treated with tetracyclines (photo-onycholysis), doxorubicin, 5-fluorouracil, cardiovascular drugs (particularly practolol and captopril), cloxacillin and cephaloridine (rarely), trimethoprim/sulfamethoxazole, diflunisal, etretinate, indomethacin, isoniazid, griseofulvin, and isotretinoin. Partial onycholysis may also result from infection with Candida albicans as a component of onychomycosis or from trauma. Partial onycholysis may occur in patients with psoriasis or thyrotoxicosis.
In this disorder, patients pick at and self-mutilate their nails, which can lead to parallel transverse grooves and ridges (washboard deformity or habit-tic nail deformity). It most commonly manifests in patients who habitually push back the cuticle on one finger, causing dystrophy of the nail plate as it grows. Subungual hemorrhages can also develop in onychotillomania.
Pincer nail deformity:
Pincer nail deformity is a transverse over-curvature of the nail plate. It can occur in patients with psoriasis, SLE, Kawasaki disease, cancer,end-stage renal disease, and some genetic syndromes (eg, as paronychia congenita). Patients often have pain at the borders of the nail where the nail plate curves into the tips of the fingers.
Subungual hematoma and nail bed trauma:
Subungual hematoma occurs when blood becomes trapped between the nail plate and nail bed, usually as a result of trauma. Subungual hematoma causes significant and throbbing pain, bluish black discoloration, and, unless small, eventual separation of and temporary loss of the nail plate. When the cause is a crush injury, underlying fracture and nail bed damage are common. Nail bed damage may result in permanent nail deformity.
If the injury is acute, nail trephination (eg, creating a hole in the nail plate using a cautery device, 18-gauge needle, or red-hot paperclip) can help relieve pain by draining accumulated blood. It is not clear whether removing the nail and repairing any nail bed damage reduces risk of permanent nail deformity.
Trachyonychia (rough, opaque nails) may occur with alopecia areata, lichen planus, atopic dermatitis, and psoriasis. It is most common among children. When present in all nails, trachyonychia is often called 20-nail dystrophy.
Benign and malignant tumors can affect the nail unit, causing deformity. These tumors include benign myxoid cysts, pyogenic granulomas, glomus tumors, Bowen disease, squamous cell carcinoma, and malignant melanoma. When cancer is suspected, expeditious biopsy followed by referral to a surgeon is strongly advised.
Last full review/revision November 2013 by Wingfield E. Rehmus, MD, MPH
Content last modified November 2013