The Nail Fold

Nail fold telangiectasia is present in a number of disorders. Dilated capillary loops in patients with collagen vascular disease can be appreciated more easily if they are visualized through a drop of oil placed on the nail fold and viewed with an ophthalmoscope set at + 40 (× 10). Thick "sausage" vessels in a bushy pattern are characteristic of dermatomyositis, scleroderma, and Raynaud's phenomenon; thinner, more meandering vessels are associated with systemic lupus erythematosus.

Bywaters" lesions are characterized as small, painless, reddish-brown infarcts in the nail fold (Figure 108.2), which may darken and fall off, leaving a tiny pitlike depression. Vasculitis, especially rheumatologic, produces these lesions.

Figure 108.2

Bywater's lesion.

Paronychia, swelling and inflammation of the proximal or lateral nail folds, can be acute or chronic. An acute paronychia represents an abscess or cellulitis usually preceded by a traumatic event. Chronic paronychia is usually related to moisture. The onset is vague, it may cause matrix abnormalities leading to Beau's lines, and it is usually associated with an absent cuticle creating an excellent entry site for Candida.

Warts are the most common tumor of the nail fold. Verrucous in quality, these can be easily differentiated from the smooth, round appearance of a myxoid cyst. Smooth, more linear, periungual angiofibromas (Koenen's tumors) can be seen in 50% of patients with tuberous sclerosis. Skin malignancies are also found in the nail fold.

The Lunula

The normally white lunula may become blue in Wilson's disease or argyria. The lunula may become red in cardiac failure or carbon monoxide poisoning.

The lunula normally increases in size in fingers closest to the thumb; however, the lunula becomes smaller or absent in old age.

The Nail Bed

A thin, 0.5 to 3.0 mm, red to brown distal transverse band characterizes Terry's nails (Figure 108.3). When the proximal pallorous nail bed is congested with blood by manually occluding venous outflow, this band must still be easily distinguishable. Terry's nails normally occur in older patients, but suspicion of cirrhosis, chronic congestive heart failure, and adult-onset diabetes mellitus should be raised in younger patients. Vascular telangiectasias in the distal nail bed produce the color change.

Figure 108.3

Terry's nail.

A brown distal band occupying approximately 20 to 50% of the nail bed, termed Lindsay's nail (half and half nail), is associated with chronic renal failure (Figure 108.4). Abnormal melanin pigment may be responsible for the disorder.

Figure 108.4

Lindsay's nail.

In Muehrcke's nail, edema of the nail bed causes characteristic pale transverse bands when the serum albumin falls below 2.2 gm/dl (Figure 108.5). Muehrcke lines disappear when the serum albumin surpasses 2.2 gm/dl.

Figure 108.5

Muehrcke's nail.

Splinter hemorrhages are an important diagnostic sign. The vascular nail bed is organized into parallel longitudinal dermal ridges oriented along the axis of nail growth. If the blood vessels in these ridges are disrupted, a small amount of hemorrhage fills the valley between two ridges, giving the characteristic appearance of a splinter. Splinter hemorrhages are most commonly associated with light trauma; however, when associated with fever and cardiac murmur, bacterial endocarditis must be suspected. Cirrhosis, vasculitis, and scurvy will also produce splinter hemorrhage, but when all nails are simultaneously affected, trichinosis becomes an important consideration.

Carbon monoxide poisoning produces cherry red nail beds due to bright red carboxyhemoglobin. Polycythemia will also produce a red-appearing nail bed, just as anemia produces pallor.

Separation of the nail bed from the overlying plate creates a white-appearing proximal extension of free air, termed onycholysis. The space may fill with dirt, accentuating the change. Both exogenous and endogenous (systemic and dermatologic disease) etiologies should be considered. Trauma, maceration, Pseudomonas, fungal infection, chemicals, and nail cosmetics can cause this separation. Photo-induced onycholysis can be caused by tetracycline derivatives, oral contraceptives, and chlorpromazine. Systemic endocrine causes of onycholysis are hypothyroidism, thyrotoxicosis (usually of the fourth finger), pregnancy, and diabetes mellitus. Hyperkeratotic plaques of psoriasis can push the overlying plate away from the bed.

The Hyponychium

The hyponychium is at the most distal region of the nail bed and marks the transition to normal skin. Tumors such as warts or Koenen's subungual angiofibromas of tuberous sclerosis are seen in the hyponychium. Fungi enter the nail unit in this area, causing onychomycosis.

The Nail Plate

Leukonychia (opaque white discoloration) may be linear (Mees" lines), punctate, or diffuse. Mees" lines are transverse white lines present in the same relative position on more than one nail (Figure 108.6). Many systemic conditions can cause an insult to the matrix, which in turn produces abnormal nucleated cells, creating a white appearance in a normally transparent plate. Classically, arsenic produces Mees" lines; however, these white lines can also be produced by other pharmacologic, infectious, or systemic assaults on nail plate-forming cells. Local trauma to an isolated area of the matrix most commonly produces a punctate leukonychia. Congenital conditions or fungus produce diffuse whitening of the plate.

Figure 108.6

Mees" lines.

A small focus of pigment-producing cells in the nail matrix will deposit pigment into the section of plate it produces, creating a longitudinal brown band oriented along the direction of nail growth. Longitudinal brown streaks are most commonly seen in junctional nevi in the matrix of black patients (Figure 108.7). However, a nevus presenting in an older white patient is very unusual. A search for generalized hyperpigmentation, especially in the palmar creases and in the oral mucosa, must be performed when considering adrenal insufficiency. Digital and perioral melanotic macules in association with longitudinal brown streaks can be seen in Peutz-Jeghers syndrome. If no underlying association can be found, malignant melanoma must be considered as a cause.

Figure 108.7

Junction nevus.

Other discolorations may occur from a variety of causes. Diffuse yellowing of the nail plate is seen in yellow nail syndrome, a condition associated with lymphedema and pulmonary complications. Diffuse brown discoloration can be found in patients with acanthosis nigricans, adrenal insufficiency, or in patients on cancer chemotherapeutics. Brownish discoloration is seen in cigarette smokers due to local deposits of nicotine and tar. Silver-blue nail plates are associated with Wilson's disease, argyria, and antimalarial drug use. Pyocyanin production by Pseudomonas will tint the plate green.

Clubbing (Hippocratic nail) occurs when local cyanosis produces hypervascularity beneath the nail matrix, elevating it further above underlying bone. In doing so, the angle between the proximal nail fold and nail plate (Lovibond's angle) exceeds 180 degrees (Figure 108.8). A bulbous "watchglass" appearance accompanies this change. Clubbing may be familial or it may be acquired, most commonly due to a hypoxia-associated thoracic condition. Chronic, infectious, or malignant bronchopulmonary disease or cardiovascular disease is often implicated. Less frequent causes are cirrhosis and inflammatory bowel diseases.

Figure 108.8

Clubbing.

A characteristic concave koilonychia (spoon nail) may be inherited or acquired. Iron deficiency anemia and other hematologic conditions, syphilis, and thyroid disease are acquired disease states producing koilonychia.

During a significant illness or infection, matrix function diminishes producing a thinner than normal plate. Following resolution of the illness, matrix function returns to normal. The transverse depression produced, termed a Beau's line (Figure 108.9), grows out, with nail growth enabling the observer to date the original illness. Febrile and infectious disease states, dermatologic disease, treatment with anti-mitotic drugs, myocardial infarction, and surgical operations are associated with Beau's lines.

Figure 108.9

Beau's line.

Pitting has several causes. Focal abnormal keratinization of the nail plate leaves pitlike depressions in patients with psoriasis. Pitting is less irregular, more geometric, and shallower in patients with alopecia areata or eczematous dermatitis.

Onychorrhexis (longitudinal ridging) in the nail plate due to irregularities in matrix shape are seen in nails of the elderly and in patients with rheumatoid arthritis (Figure 108.10). Ridges may take on a beaded "sausage link" appearance in older patients.

Figure 108.10

Onychorrhexis.

Onychogryphosis occurs when the nail plate thickens, the nail bed is hyperkeratotic, and uneven growth occurs at the matrix. The thick nail grows spirally like a ram's horn. Onychogryphosis occurs commonly in the elderly but can occur in younger patients in onychomycosis or due to matrix injury.

Fungal infection entering from the distal nail can cause disruption of the plate, friability, and destruction. Abnormal keratinization in psoriasis produces a similar pattern.