Careful examination of the fingernails and toenails can provide clues to underlying systemic diseases. Findings may provide important clues to the diagnosis of the cause of illness, limit the differential diagnosis, and help focus on further work-up.
YELLOW NAIL SYNDROME
Yellow nail syndrome is a syndrome in which nails grow more slowly and develop a thickened appearance. The lateral sides of the nail plate show exaggerated convexity, the lunula disappears, and the nail takes on a yellow hue.
This syndrome may be seen in patients with chronic bronchiectasis or sinusitis, pleural effusions, internal malignancies, immunodeficiency syndromes, and rheumatoid arthritis. When it occurs in patients with rheumatoid arthritis, yellow nail syndrome commonly is found in the patients treated with thiol drugs; these medications are thought to play a role in the nail condition.
Clubbing of the nails is a thickening of the soft tissue beneath the proximal nail plate that results in sponginess and thickening in the area. The angle between the finger proximal to the nail and the proximal nail plate is straightened, creating the “Schamroth sign,” which is an obliteration of the normally diamond-shaped space formed when dorsal sides of the distal phalanges of corresponding right and left digits are opposed.
Clubbing occurs in patients with neoplastic diseases, particularly those of the lung. It may also accompany other pulmonary diseases, including bronchiectasis, lung abscess, empyema, pulmonary fibrosis, and cystic fibrosis. Arteriovenous malformations or fistulas have been associated with clubbing, as have celiac disease, cirrhosis, and inflammatory bowel disease. Clubbing also may occur in patients with congenital heart disease and endocarditis.
Koilonychia is represented by transverse and longitudinal concavity of the nail, resulting in a “spoon-shaped” nail. This abnormality is sometimes a normal nail variant in infants, but it usually corrects itself within the first few years of life. Koilonychia also may result from trauma, constant occupational exposure of the hands to petroleum-based solvents, or nail-patella syndrome. Koilonychia has been associated with iron deficiency, with or without anemia, Raynaud’s disease and lupus erythematosus.
Nail pitting has punctate depressions in the nail plate. Pitting usually is associated with psoriasis, affecting 10 to 50 percent of patients with that disorder. Pitting also may be caused by a variety of systemic diseases, including Reiter’s syndrome, sarcoidosis, pemphigus, alopecia areata, and incontinentia pigmenti. In addition, any localized dermatitis that disrupts orderly growth in that area also can cause pitting.
Onycholysis, which occurs when the nail plate is separated from the nail bed, results in white discoloration of the affected area. It can be caused by any local problem, such as periungual warts or onychomycosis that separates the nail plate from the bed, although the most common reason for this separation is trauma. Separation may result if the nail is lifted mechanically off the bed or if a blow to the nail causes bleeding between the nail and the bed. Onycholysis can accompany psoriasis or if no clear local cause is discovered, a diagnosis of hyperthyroidism should be considered.
TRANSVERSE LINEAR LESIONS
Transverse linear depressions in the nail plate are called Beau’s lines. Beau’s lines occur at the same spot of the nail plate in most or all of the person’s nails and may be caused by any disease severe enough to disrupt normal nail growth. Other causes of Beau’s lines include trauma and exposure to cold temperatures in patients with Raynaud’s disease.
Mees’ lines are transverse white bands that frequently affect multiple nails, although they also may occur singly. They are most often seen with arsenic poisoning, thallium or other heavy metals, and can also appear if the subject is suffering from renal failure or in chemotherapy patients. In patients with Mees’ lines, the nail bed is normal, but the nail itself is microscopically fragmented, due to the disruption of normal growth at the nail matrix. The width of the lines varies and, because the defect is in the nail itself, the line moves distally with time.
Pairs of transverse white lines that extend all the way across the nail are called Muehrcke’s lines. The lines represent an abnormality of the vascular nail bed and disappear while the nail is depressed and blood is squeezed from the vessels beneath the nail. Because the lesion is in the nail bed, it does not move with nail growth. These characteristics distinguish Muehrcke’s lines from Mees’ lines. Muehrcke’s lines occur in patients with hypoalbuminemic states and disappear when the protein level normalizes. They also may be present in patients with nephrotic syndrome, liver disease, and malnutrition.
Children and active adults commonly have one or more white lines or spots on one or more nails; this condition is known as leukonychia. These lines and spots are nonuniform, appear in different places on different nails, do not span the nail, and are of no significance. They are thought to result from random minor trauma to the proximal nail bed. Unlike leukonychia, Mees’ and Muehrcke’s lines are always parallel to the edge of the lunula.
Longitudinal Linear Lesions
Longitudinal pigmented bands are normal findings in the nails of dark-skinned persons, occurring in more than 77% of African Americans older than 20 years. These findings present a diagnostic problem because they must be differentiated from subungual melanomas, which also occur in older age groups and constitute 50% of melanomas in dark-skinned populations. Nail symptoms in patients with increased likelihood should be considered melanoma until proved otherwise by a punch biopsy.
Longitudinal striations are accentuated ridges in the nail surface that can occur as a normal part of the aging process. If nails become thin and lusterless the condition may be referred to as trachyonychia. In this situation, associated conditions, including alopecia areata, psoriasis, atopic dermatitis, vitiligo, and lichen planus, must be considered.
Nail Bed and Vascular Changes
Splinter hemorrhages are longitudinal thin lines, red or brown in color, which occurs beneath the nail plate. They are visible when capillaries leak. While splinter hemorrhages may signify benign problems such as local trauma, psoriasis, or localized fungal infection, they are a classic finding in patients with endocarditis.
Splinter hemorrhages are thought to be a more specific indicator of endocarditis if they are present proximally rather than distally on the nail plate, and they are more common in subacute than acute infection. However, splinter hemorrhages occur in only about 15% of patients with endocarditis and may be present in up to 20% of persons without endocarditis. The causes of splinter hemorrhage are so varied and common that their usefulness as an isolated sign of illness has been questioned. Examination of the capillaries at the eponychium normally shows an orderly array of parallel vessels. In patients with rheumatoid arthritis, systemic lupus erythematosus, dermatomyositis, or scleroderma, examination of the capillaries show irregular, twisted, and dilated vessels attributing to the erythematous appearance of the nail.
In patients with Wilson’s disease (hepatolenticular degeneration), the lunula takes on a blue coloration. Heart failure can turn the lunula red, and tetracycline therapy can turn it yellow. Silver poisoning will turn the nail itself a blue-gray color. Excessive fluoride ingestion can turn nails brown or black.
In patients with Terry’s nails, most of the nail plate turns white with the appearance of ground glass, and the lunula is obliterated. This condition was described originally in relation to severe liver disease, usually cirrhosis. Terry’s nails are also seen in conditions thought to be caused by a decrease in vascularity and an increase in connective tissue in the nail bed.
Similarly, in patients with chronic renal failure, increased melanin production may cause the distal part of the nail bed to turn brown. In patients with severe renal disease, the proximal portion of the nail bed can turn white, obliterating the lunula and giving a half-brown, half-white appearance.