Abnormalities in Nail Shape or Size

Anonychia is absence of the nail plate, usually a result of a congenital disorder or trauma. It may be an isolated finding or may be associated with malformations of the digits. Koilonychia is flattening and concavity of the nail plate with loss of normal contour, producing a spoon-shaped nail (Fig. 655-1). Koilonychia occurs as an autosomal dominant trait or in association with iron deficiency anemia, Plummer-Vinson syndrome, or hemochromatosis. The nail plate is relatively thin for the first year or two of life and, consequently, may be spoon-shaped in otherwise normal children.

Figure 655-1 Spoon nails (koilonychia). Most cases are a variant of normal.

(From Habif TP, editor: Clinical dermatology, ed 4, Philadelphia, 2004, Mosby, p 885.)

Congenital nail dysplasia, an autosomal dominant disorder, manifests at birth as longitudinal streaks and thinning of the nail plate. There is platyonychia and koilonychia, which may overgrow the lateral folds and involve all nails of the toes and fingers.

Nail-patella syndrome is an autosomal dominant disorder in which the nails are 30-50% of their normal size and often have triangular or pyramidal lunulae. The thumbnails are always involved, although in some cases only the ulnar half of the nail may be affected or may be missing. The nails from the index finger to the little finger are progressively less damaged. The patella is also smaller than usual, and this anomaly may lead to knee instability. Bony spines arising from the posterior aspect of the iliac bones, overextension of joints, skin laxity, and renal anomalies may also be present. Nail-patella syndrome is caused by mutations in the transcription factor LMX1B gene.

For a discussion of pachyonychia congenita, see Chapter 650.

Habit tic deformity consists of a depression down the center of the nail with numerous horizontal ridges extending across the nail from it. One or both thumbs are usually involved as a result of chronic rubbing and picking at the nail with an adjacent finger.

Clubbing of the nails (hippocratic nails) is characterized by swelling of each distal digit, an increase in the angle between the nail plate and the proximal nail fold (Lovibond angle) to >180 degrees, and a spongy feeling when one pushes down and away from the interphalangeal joint, because of an increase in fibrovascular tissue between the matrix and the phalanx (Fig. 655-2). The pathogenesis is not known. Nail clubbing is seen in association with diseases of numerous organ systems, including pulmonary, cardiovascular (cyanotic heart disease), gastrointestinal (celiac disease, inflammatory bowel disease), and hepatic (chronic hepatitis) systems, as well as in healthy individuals as an idiopathic or familial finding.

Figure 655-2 Finger clubbing. The distal phalanges are enlarged to a rounded bulbous shape. The nail enlarges and becomes curved, hard, and thickened.

(From Habif TP, editor: Clinical dermatology, ed 4, Philadelphia, 2004, Mosby, p 885.)

Changes in Nail Color

Leukonychia is a white opacity of the nail plate that may involve the entire plate or may be punctate or striate (see Table 655-1). The nail plate itself remains smooth and undamaged. Leukonychia can be traumatic or associated with infections such as leprosy and tuberculosis, dermatoses such as lichen planus and Darier disease, malignancies such as Hodgkin disease, anemia, and arsenic poisoning (Mees lines). Leukonychia of all nail surfaces is an uncommon hereditary autosomal dominant trait that may be associated with congenital epidermal cysts and renal calculi. Paired parallel white bands that do not change position with growth of the nail and thus reflect a change in the nail bed are associated with hypoalbuminemia and are called Muehrcke lines. When the proximal portion of the nail is white and the distal 20-50% of the nail is red, pink, or brown, the condition is called half-and-half nails or Lindsay nails; this is seen most commonly in patients with renal disease but may occur as a normal variant. White nails of cirrhosis, or Terry nails (Fig. 655-3), are characterized by a white ground-glass appearance of the entire or the proximal end of the nail and a normal pink distal 1-2 mm of the nail; this finding is associated with hypoalbuminemia.

Figure 655-3 Terry nails. The nail bed is white with only a narrow zone of pink at the distal end.

(From Habif TP, editor: Clinical dermatology, ed 4, Philadelphia, 2004, Mosby, p 885.)

Black pigmentation of an entire nail plate or linear bands of pigmentation (melanonychia striata) is common in black (90%) and Asian (10-20%) individuals but is unusual in white individuals (<1%). Most often, the pigment is melanin, which is produced by melanocytes of a junctional nevus in the nail matrix and nail bed and is of no consequence. Extension or alteration in the pigment should be evaluated by biopsy because of the possibility of malignant change.

Bluish black to greenish nails may be caused by Pseudomonas infection (Fig. 655-4), particularly in association with onycholysis or chronic paronychia. The coloration is due to subungual debris and pyocyanin pigment from the bacterial organisms.

Figure 655-4 Green/black discoloration at the edge of the nails secondary to Pseudomonas infection.

Yellow nail syndrome manifests as thickened, excessively curved, slow-growing yellow nails without lunulae. All nails are affected in most cases. Associated systemic diseases include bronchiectasis, recurrent bronchitis, chylothorax, and focal edema of the limbs and face. Deficient lymphatic drainage, due to hypoplastic lymphatic vessels, is believed to lead to the manifestations of this syndrome.

Splinter hemorrhages most often result from minor trauma but may also be associated with subacute bacterial endocarditis, vasculitis, Langerhans cell histiocytosis, severe rheumatoid arthritis, peptic ulcer disease, hypertension, chronic glomerulonephritis, cirrhosis, scurvy, trichinosis, malignant neoplasms, and psoriasis.

Nail Separation

Onycholysis indicates separation of the nail plate from the distal nail bed. Common causes are trauma, long-term exposure to moisture, hyperhidrosis, cosmetics, psoriasis, fungal infection (distal onycholysis), atopic or contact dermatitis, porphyria, drugs (bleomycin, vincristine, retinoid agents, indomethacin, chlorpromazine [Thorazine]), and drug-induced phototoxicity from tetracyclines (Fig. 655-5) or chloramphenicol.

Figure 655-5 Distal onycholysis secondary to oral tetracycline usage and ultraviolet light exposure.

Beau lines are transverse grooves in the nail plate (Fig. 655-6) that represent a temporary disruption of formation of the nail plate. The lines first appear a few weeks after the event that caused the disruption in nail growth. A single transverse ridge appears at the proximal nail fold in most 4- to 6-wk-old infants and works its way distally as the nail grows; this line may reflect metabolic changes after delivery. At other ages, Beau lines are usually indicative of periodic trauma or episodic shutdown of the nail matrix secondary to a systemic disease such as hand-foot-and-mouth disease, measles, mumps, pneumonia, or zinc deficiency. Onychomadesis is an exaggeration of Beau lines leading to proximal separation of the nail bed (Fig. 655-7).

Figure 655-6 Beau lines. Longitudinal disruption of nail.

Figure 655-7 Onychomadesis. Proximal nail bed separation.

Nail Changes Associated with Skin Disease

Nail changes may be particularly associated with various other diseases. Nail changes of psoriasis most characteristically include pitting, onycholysis, yellow-brown discoloration, and thickening. Nail changes in lichen planus include violaceous papules in the proximal nail fold and nail bed, leukonychia, longitudinal ridging, thinning of the entire nail plate, and pterygium formation, which is abnormal adherence of the cuticle to the nail plate or, if the plate is destroyed focally, to the nail bed. Postinfectious reactive arthritis syndromes may include painless erythematous induration of the base of the nail fold; subungual parakeratotic scaling; and thickening, opacification, or ridging of the nail plate. Dermatitis that involves the nail folds may produce dystrophy, roughening, and coarse pitting of the nails. Nail changes are more common in atopic dermatitis than in other forms of dermatitis that affect the hands. Darier disease is characterized by red or white streaks that extend longitudinally and cross the lunula. Where the streak meets the distal end of the nail, a V-shaped notch may be present. Total leukonychia may also occur. Transverse rows of fine pits are characteristic of alopecia areata. In severe cases, the entire nail surface may be rough. Patients with acrodermatitis enteropathica may have transverse grooves (Beau lines) and nail dystrophy as a result of periungual dermatitis.

Trachyonychia (20-nail Dystrophy)

Trachyonychia is characterized by longitudinal ridging, pitting, fragility, thinning, distal notching, and opalescent discoloration of all the nails (Fig. 655-8). Patients have no associated skin or systemic diseases and no other ectodermal defects. Its occasional association with alopecia areata has led some authorities to suggest that trachyonychia may reflect an abnormal immunologic response to the nail matrix, whereas histopathologic studies have suggested that it may be a manifestation of lichen planus, psoriasis, or spongiotic (eczematous) inflammation of the nail matrix. The disorder must be differentiated from fungal infections, psoriasis, nail changes of alopecia areata, and nail dystrophy secondary to eczema. Eczema and fungal infections rarely produce changes in all the nails simultaneously. The disorder is self-limited and eventually remits by adulthood.

Figure 655-8 Dystrophy of all nails in trachyonychia.

Nail Infection

Fungal infection of the nails has been classified into 4 types. White superficial onychomycosis manifests as diffuse or speckled white discoloration of the surface of the toenails. It is caused primarily by Trichophyton mentagrophytes, which invades the nail plate. The organism may be scraped off the nail plate with a blade, but treatment is best accomplished by the addition of a topical azole antifungal agent. Distal subungual onychomycosis involves foci of onycholysis under the distal nail plate or along the lateral nail groove, followed by development of hyperkeratosis and yellow-brown discoloration. The process extends proximally, resulting in nail plate thickening, crumbling (Fig. 655-9), and separation from the nail bed. Trichophyton rubrum and, occasionally, T. mentagrophytes infect the toenails; fingernail disease is almost exclusively due to T. rubrum, which may be associated with superficial scaling of the plantar surface of the feet and often of one hand. The dermatophytes are found most readily at the most proximal area of the nail bed or adjacent ventral portion of the involved nail plates. Topical therapies such as ciclopirox 8% lacquer may be effective for solitary nail infection. Because of its long half-life in the nail, either terbinafine or itraconazole may be effective when given as pulse therapy (1 wk of each month for 3-4 mo). Dosage is weight dependent. Either agent is superior to griseofulvin, fluconazole, or ketoconazole. The risks, the most concerning of which is hepatic toxicity, and costs of oral therapy are minimized with the use of pulsed dosing.

Figure 655-9 Discoloration, hyperkeratosis, and crumbling of nail secondary to dermatophyte infection.

Proximal white subungual onychomycosis occurs when the organism, generally T. rubrum, enters the nail through the proximal nail fold, producing yellow-white portions of the undersurface of the nail plate. The surface of the nail is unaffected. This occurs almost exclusively in immunocompromised patients and is a well-recognized manifestation of AIDS. Treatment includes oral terbinafine or itraconazole.

Candidal onychomycosis involves the entire nail plate in patients with chronic mucocutaneous candidiasis. It is also commonly seen in patients with AIDS. The organism, generally Candida albicans, enters distally or along the lateral nail folds, rapidly involves the entire thickness of the nail plate, and produces thickening, crumbling, and deformity of the plate. Topical azole antifungal agents may be sufficient for treatment of candidal onychomycosis in an immunocompetent host, but oral antifungal agents are necessary for treatment of patients with immune deficiencies.

Paronychial Inflammation

Paronychial inflammation may be acute or chronic and generally involves 1 or 2 nail folds on the fingers. Acute paronychia manifests as erythema, warmth, edema, and tenderness of the proximal nail fold, most commonly as a result of pathogenic staphylococci or streptococci (Fig. 655-10). Warm soaks and oral antibiotics are generally effective; incision and drainage may be occasionally necessary. Development of chronic paronychia follows prolonged immersion in water (Fig. 655-11), such as occurs in finger or thumb sucking, exposure to irritating solutions, nail fold trauma, or diseases, including Raynaud phenomenon, collagen vascular diseases, and diabetes. Swelling of the proximal nail fold is followed by separation of the nail fold from the underlying nail plate and suppuration. Foreign material, embedded in the dermis of the nail fold, becomes a nidus for inflammation and infection with Candida species and mixed bacterial flora. A combination of attention to predisposing factors, meticulous drying of the hands, and long-term topical antifungal agents and topical potent corticosteroids may be required for successful treatment of chronic paronychia.

Figure 655-10 Acute paronychia secondary to Staphylococcus aureus.

Figure 655-11 Chronic paronychia with erythema and lateral nail fold separation.

Ingrown nail occurs when the lateral edge of the nail, including spicules that have separated from the nail plate, penetrates the soft tissue of the lateral nail fold. Erythema, edema, and pain, most often involving the lateral great toes, are noted acutely; recurrent episodes may lead to formation of granulation tissue. Predisposing factors include (1) congenital malalignment (especially of the great toes); (2) compression of the side of the toe from poorly fitting shoes, particularly if the great toes are abnormally long and the lateral nail folds are prominent; and (3) improper cutting of the nail in a curvilinear manner rather than straight across. Management includes proper fitting of shoes; allowing the nail to grow out beyond the free edge before cutting it straight across; warm water soaks; oral antibiotics if cellulitis affects the lateral nail fold; and, in severe, recurrent cases, application of silver nitrate to granulation tissue, nail avulsion, or excision of the lateral aspect of the nail followed by matricectomy.

Paronychial Tumors

Tumors in the paronychial area include pyogenic granulomas, mucous cysts, subungual exostoses, and junctional nevi. Periungual fibromas that appear in late childhood should suggest a diagnosis of tuberous sclerosis.