Disorders of Nails

Liborka Kos

Nail abnormalities are commonly an isolated benign finding related to infection or trauma. Occasionally, a nail change is a manifestation of an underlying generalized skin disorder, a systemic disease, or a congenital syndrome. Nail problems are often difficult to diagnose and are notoriously difficult to treat. Knowledge of nail anatomy is essential for an understanding of nail disease (see Fig. 356-2). The nail plate is firmly attached to the vascularized, innervated nail bed by two parallel, longitudinal grooves at either side. The cuticle firmly attaches to the proximal nail plate, preventing water, bacteria, and other irritants from entering the area of nail synthesis, the nail matrix.

Oncycholysis is separation of the nail plate from the nail bed. It may be caused by trauma, psoriasis, certain medications, and fungal or yeast infections (eFig. 366.1 ). When evaluating onycholysis, obtaining a history of trauma, thumb sucking or other chronic wet exposures, medications, and other cutaneous lesions is important. Onycholysis often responds to trimming back the nail, avoidance of frequent contact with water, and use of a topical anticandidal agent.

In koilonychia, affected nails are concave or “spoon shaped” (eFig. 366.2 ). Koilonychia may occur as an autosomal-dominant trait or in association with iron deficiency, hypothyroidism, hemochromatosis, or lichen planus. When present in infancy as an isolated finding, the process resolves with time.

Nail pitting (punctate depressions in the nail plate) reflects an abnormality of growth in the proximal nail matrix with imperfect nail plate formation and focal loss of keratin. In children, pitting is usually seen in association with psoriasis (eFig. 366.3 ), alopecia areata, or eczema. An occasional pit may be present as a normal variant.

Clubbing, long recognized as a manifestation of cardiac and pulmonary disease, is defined as a reduction of the obtuse angle between the cuticle and nail bed. In children, congenital cyanotic heart disease, cystic fibrosis, and inflammatory bowel disease are the most frequent causes.

Horizontal ridging is commonly seen with inflammation of the proximal nail fold, as in candidal paronychia or atopic dermatitis. Beau lines are horizontal grooves resulting from abrupt, temporary cessation of nail growth due to a systemic illness or medication (eFig. 366.4 ).Onychomadesis, similarly, is complete separation of the nail plate due to full matrix arrest secondary to a systemic illness, medication, or other stressor (eFig. 366.5 ). Longitudinal grooves may result from any process causing inflammation in the nail matrix, including trauma, lichen planus, psoriasis, alopecia area-ta, Darier disease, Langerhans cell histiocytosis, and graft-versus-host disease. Wide longitudinal grooves may be caused by growths (usually visible) pressing on the matrix, such as large periungual warts, digital mucous cysts, or the periungual fibromas of tuberous sclerosis (eFig. 366.6 ).

Median nail dystrophy is characterized by a longitudinal groove or fissure in the center of the nail plate, usually the thumbnail. Splits and grooves radiate from the central groove, resembling a fir tree (eFig. 366.7 ).

Trachyonychia manifests with multiple pits, longitudinal ridging, and a typical sandpaperlike appearance (eFig. 366.8 ). Twenty nail dystrophy is the term used when most or all digits are involved (eFig. 366.9 ). It usually develops in children and typically resolves over several years. Trachyonychia can be seen as an isolated finding or in association with psoriasis, lichen planus, alopecia areata, and eczema.¹

CONGENITAL NAIL ABNORMALITIES

Congenital nail abnormalities may occur as isolated defects or part of a more generalized syndrome. Many neonates appear to have ingrown nails distally. This is a common phenomenon that resolves spontaneously during the first year of life. Congenital malalignment of the great toe-nails is seen in newborns whose nail matrix and the nail plate it produces deviate laterally and do not align with the nail bed (eFig. 366.10 ). It is self-limited in some infants, but persists in others, in which case surgical intervention is required to prevent chronic ingrowing.^7,8

Pachyonychia congenita is transmitted as an autosomal-dominant trait. The nails are thickened and yellow-brown, with an increased curvature and subungual hyperkeratosis (eFig. 366.11 ). Associated findings may include palmoplantar keratoderma, oral leukokeratosis, and steatocystoma multiplex.

Nail abnormalities associated with ectodermal dysplasias may be obvious at birth or have a later age of onset (eFigs. 366.12 and 366.13 ). Nail dystrophy is the predominant feature of hidrotic ectodermal dysplasia, an autosomal-dominant disorder also characterized by hyperkeratosis of the palms and soles and hair defects.

Micronychia (small nails) may be seen in the nail-patella syndrome, inherited as an autosomal-dominant trait. Other features include triangular lunulae, absent or hypoplastic patellae, nephrosis, and occasional ophthalmologic and central nervous system abnormalities.

DISCOLORATION OF THE NAIL

Discoloration of the nail can be due to staining from an external agent, deposition of pigment within the nail plate, or pigment in the nail bed. Exogenous pigment, such as the yellow staining seen in smokers, typically follows the shape of the cuticle.

Trauma to the nail can lead to the development of a subungual hematoma and subsequent brown-black pigmentation in the nail bed. Chronic trauma or pressure on the toenails may also lead to similar deposition of pigment following hemorrhage within the area. White discoloration (leuconychia) is common. Transverse or punctate white areas are usually a result of trauma, but may be familial. Half-and-half nails (Lindsey nails) consist of white discoloration of the proximal nail and red coloration of the distal portion, and are seen with uremia. Terry nails, with white discoloration of all but a few millimeters of the distal edge, are associated with cirrhosis or congestive heart failure (eFig. 366.14 ). Paired horizontal white bands, or Muehrcke lines, are seen with hypoalbuminemia and chemotherapy, whereas Mee lines, transverse 1- to 2-mm white bands, are due to arsenic, thallium, or lead poisoning. Longitudinal brown or black pigmented bands (melanonychia striata) may indicate the presence of a melanocytic nevus or lentigo in the nail matrix (eFig. 366.15 ). Such bands are common in darkly pigmented races, but unusual in whites. A solitary pigmented band that suddenly changes in color or becomes wider may warrant a nail matrix biopsy to exclude melanoma, even in an Asian or black individual.¹⁰ Extension of the pigment over the proximal nail fold (Hutchinson sign) is also suspicious for melanoma.

Blue discoloration of the lunulae may be seen in Wilson disease and with administration of zidovudine. Brown or black discoloration can be caused by drugs, such as doxorubicin, zidovu-dine, antimalarials, and minocycline. The yellow nail syndrome, rare in children, consists of thickened yellow nails, lymphedema, and respiratory disease. Yellow nails may also be seen with thyroid disease, nephrotic syndrome, immunoglobulin A deficiency, and mental retardation.

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