Chapter 68 Nail disorders
2. Why are nails important in medicine?
Nails are important because they are easily observable and serve as a window into the body. They are commonly affected by numerous internal (heart, liver, kidney) and external factors, including infectious agents, trauma, and drugs. Finally, nails may help in the differential diagnosis of closely related dermatologic disorders.
3. Do any systemic diseases have specific nail findings?
Many systemic diseases have characteristic, but not mutually exclusive, nail findings. Most nail changes are part of a symptom complex or a reaction pattern that may be extremely helpful in making a particular diagnosis (Table 68-1).
Table 68-1. Nail Disorders in Systemic Disease
| NAIL ABNORMALITY | AREA INVOLVED | ASSOCIATED DISEASE |
|---|---|---|
| Splinter hemorrhages | Bed | Bacterial endocarditis |
| Mees’ lines | Plate | Arsenic exposure |
| Muehrcke’s lines | Bed | Nephrotic syndrome |
| Terry’s nails | Bed | Cirrhosis |
| Half-and-half nails | Bed | Chronic renal failure |
| Blue lunulae | Matrix | Wilson’s disease |
| Red lunulae | Matrix | Rheumatoid arthritis |
| Clubbing | Plate/matrix | Pulmonary disorders |
| Spoon nails | Plate/matrix | Iron deficiency |
| Nail fold telangiectasias | Nailfold | Scleroderma, systemic lupus |
| Yellow nails | Plate | Pulmonary disorders, sinusitis |
Scher RK, Daniel CR: Nails: therapy, diagnosis, surgery, ed 3: Philadelphia, 2005, WB Saunders.
4. What are Beau’s lines? How are they formed?
Beau’s lines represent the most common but least specific nail changes seen with systemic diseases. They are a forward-pointing, wedge-shaped depression in the nail plate of variable depth and obliquity. They occur when there is temporary cessation of nail growth or decreased deposition of nail plate by the nail matrix. Frequently, Beau’s lines are caused by mechanical trauma or diseases of the proximal nail fold. If all of the nails are affected at the same level, a systemic cause is indicated, while localized events (trauma) produce isolated lines.
5. What is a splinter hemorrhage?
A splinter hemorrhage results from the extravasation of blood from the longitudinally oriented vessels of the nail bed. The blood usually attaches to the overlying nail plate and moves distally with it. The occurrence of a hemorrhage close to the lunula and, simultaneously, in multiple nails correlates more directly with systemic disease.
6. Are splinter hemorrhages always associated with subacute bacterial endocarditis?
A commonly held, almost “sacred teaching” in medical school but rarely true. There is a myriad of causes, with subacute bacterial endocarditis representing only a small fraction. By far, simple trauma is the most common cause. Other known entities include drug reactions, general illness, vasculitis, and trichinosis, to name a few.
7. What is the difference between Mees’ lines and Muehrcke’s lines?
Mees’ lines represent single or multiple transverse white lines that occur in the nail plate and move distally as the nail grows out. They are classically thought to be caused by arsenic intoxication, but many severe systemic insults may initiate them. Muehrcke’s lines were described in 1956 by Robert C. Muehrcke in an article entitled “The Finger-nails in Chronic Hypoalbuminaemia.” These represent transverse, double, white lines that are an abnormality of the vascular bed, probably a localized edematous state secondary to the hypoalbuminemia. The underlying causes of these lines include the nephrotic syndrome, liver disease, and malnutrition.
Muehrcke RC: The finger-nails in chronic hypoalbuminaemia, Br Med J 9:1327–1328, 1956.
8. What are “half-and-half” nails, and with what internal disease are they associated?
Half-and-half nails are characterized by apparent leukonychia (white color that disappears with pressure) that affects the proximal half of the nail (Fig. 68-1). Although it may be seen in normal individuals, it is associated with patients with chronic renal disease in approximately 10% of patients.
9. What is nail fold capillaroscopy? How is it useful?
It is the in vivo examination of nail fold and cuticle finger capillaries, with magnification, to detect variations in capillary patterns. Autoimmune connective tissue disorders can have subtle but distinct changes within these capillaries and the proximal nail fold. It can be useful in predicting which patients with Raynaud’s syndrome will likely develop scleroderma. In those with scleroderma, the severity of capillary lesions may correlate with the degree of multisystem organ disease. Patients with dermatomyositis have capillary changes along with thickened, ragged cuticles. In systemic lupus, paronychial inflammation may be prominent with dilated tortuous capillaries distinctive.
Figure 68-1. Half-and-half nails in a patient with chronic renal disease.
(Courtesy of the Fitzsimons Army Medical Center teaching files.)
Tosti A: The nail apparatus in collagen disorders, Semin Dermatol 10:71–76, 1991.
10. What is clubbing?
Clubbing refers to the increased bilateral curvature of the nails with proliferation of the soft tissues restricted to the distal phalanges (Fig. 68-2). It causes an increase in the emergence angle of the nail to equal or greater than 180 degrees. There are diverse causes of clubbing, including congenital or genetic factors, but 80% of clubbing is associated with respiratory ailments.
11. How is hypertrophic osteoarthropathy related to clubbing?
Clubbing may occur in association with hypertrophic osteoarthropathy, an uncommon but important entity. It consists of simple clubbing (including the toes), hypertrophy of the upper and lower extremities, peripheral neurovascular disease, acute burning bone pain, joint problems, and muscle weakness. More importantly, when complete, it is associated 90% of the time with malignant tumors of the chest.
12. What is the yellow nail syndrome?
The yellow nail syndrome consists of the classic triad of lymphedema of the lower extremity, nail changes, and pleural effusion. The nails are thickened, yellowish, and curved side to side with absent lunulae and cuticles (Fig. 68-3). It is associated with a multitude of pulmonary diseases including tuberculosis, asthma, and respiratory tract cancers.
13. Are there any characteristic nail changes in primarily dermatologic diseases?
Unfortunately, because the nail unit has only limited ways of responding to pathologic insults, pathognomonic changes are seldom encountered. However, examination of the nails is imperative because there are certain changes that, viewed in context with the entire clinical picture, can help establish a diagnosis (Table 68-2).
Figure 68-3. Yellow nail syndrome, demonstrating typical thick, yellow, and curved nails.
(Courtesy of James E. Fitzpatrick, MD.)
Table 68-2. Dermatologic Disorders with Nail Changes
| DISEASE | INCIDENCE | FINDINGS |
|---|---|---|
| Psoriasis | 10%–50% | Pits, “oil spots” |
| Alopecia areata | 20%–50% | Pits |
| Lichen planus | 10% | Pterygium |
| Scleroderma | Frequent | Pterygium inversus unguium |
| Darier’s disease | High | Wedge shaped, hyperkeratosis |
| Pityriasis rubra pilaris | Majority | Yellow-brown, hyperkeratotic |
16. What other nail findings are seen in psoriasis? What is the significance of nail changes?
Psoriasis can affect all parts of the nail unit and, hence, causes a wide variety of changes in the nail that are characteristic and helpful diagnostic aids. Nail abnormalities may be the only manifestation of psoriasis. They are frequently associated with psoriatic arthropathy. In descending order of frequency, the nail findings in psoriasis are:
17. How does a pterygium differ from pterygium inversus unguium?
A pterygium, which is Greek for “wing,” is classically associated with lichen planus. Lichen planus attacks the nail-forming unit, the matrix, and causes permanent scarring. Because the nail plate at that site is no longer made, the proximal nail fold attaches to the nail bed directly, and both grow out distally. This produces the “winglike” appearance.
Pterygium inversus unguium occurs when the nail plate distally does not separate from the underlying digital bed skin. The fingertip ulcerations and scarring also seen in scleroderma contribute to the inability of the nail to separate (Fig. 68-5).
18. What is the most common cause and sequela of a subungual hematoma? How is it treated?
By far, the most common cause is trauma to the nail bed. Most subungual hematomas are accompanied by a throbbing pain secondary to the accumulation of blood below the nail plate, which exerts pressure on the underlying bed (Fig. 68-6). An effective and simple treatment is to simply pass the tip of a heated paper clip through the nail into the hematoma. Pressure relief and lessening of pain rapidly ensue, making you an instant hero!
20. How do you tell the difference between a subungual hematoma and a malignant melanoma?
This is a very important distinction to make because a melanoma can have a high mortality rate if diagnosed late. One should have a high suspicion for a melanoma, if pigment develops in a single nail of a person aged 50 to 80 years old. Also, any band in the nail that is wider at the base or darkening is worrisome. Hutchinson’s sign, the leaching of pigment into the surrounding nail fold, is considered pathognomonic. Hematoma pigment remains confined to the nail bed and gradually grows out with the nail. Melanonychia (longitudinal pigmented lines on nails) is also very common in individuals with darker skin and is a more likely diagnosis if multiple nails are affected, the lines are well demarcated laterally, they are not changing, and Hutchinson’s sign is negative.
21. What nail changes are considered peculiar to human immunodeficiency virus (HIV) infection?
Patients with acquired immune deficiency syndrome may develop acromelanosis, in which hyperpigmented macules occur on the fingers, palms, soles, and nails. In the nails, they appear as longitudinal pigmentary bands (melanonychia). Hence, melanonychia of several nails with skin hyperpigmentation is a strong clue to HIV infection. Commonly, nail pigmentation is seen with the drug zidovudine. Proximal subungual onychomycosis and candidal onychomycosis are also considered a marker for HIV infection. Long-standing, treatment-resistant, periungual warts are common, and progression to squamous cell carcinoma is a distinct possibility.
22. What is onychocryptosis? Why does it occur?
Onychocryptosis represents an ingrown toenail. It occurs when the free edge of the nail plate penetrates through the soft tissue of the nail fold. Factors that are known to precipitate or secondarily cause this condition are excessive rotation of the toe, onycholysis along the nail margin, ill-fitting shoes, hyperhidrosis, and poor cutting (rounding the edges) of the nails. Infection is a secondary complication.
23. What is a paronychia?
A paronychia is an inflammation of the nail fold surrounding the nail plate, which may occur in either an acute or chronic form. Acute forms are precipitated by some form of trauma or chemical damage and usually present as painful infections (Fig. 68-7). Chronic paronychias tend to occur in several fingers simultaneously and result from repeated wet activities. An exception to this rule is the chronic paronychia caused by the habitual sucking of a finger, which tends to favor only one finger! Primary skin conditions, eczema, and atypical infectious organisms may also contribute to chronic paronychias.
Jebson PJL: Infections of the fingertip: paronychias and felons, Hand Clin 14:547–555, 1998.
25. How do you treat an acute paronychia?
A quick and easy method to relieve pain and hasten healing is to stab the purulent area with a no. 11 scalpel blade and discharge the pus. A topical refrigerant spray to temporarily numb the area prior to incision will make for a grateful patient. Antibiotics and soaks should then be instituted, starting with coverage for Staphylococcus aureus until the culture is back.
26. What is the most common cause of green nails?
The most common cause is Pseudomonas aeruginosa, which can colonize nail plates that are abnormally lifted up. This bacterium produces a pyocyanin pigment that imparts the green discoloration. After the nail is cut away, local therapy with a topical antiseptic or antibiotics is all that is needed for a cure (Fig. 68-8).
27. What is the difference between onychomycosis and tinea unguium? What organisms most commonly cause tinea unguium? Where does the infection typically start?
Whereas onychomycosis includes all fungal infections of the nail (dermatophytes and others), tinea unguium refers specifically to dermatophyte infection of the nail. The most common organisms are Trichophyton rubrum (most common), T. mentagrophytes, and Epidermophyton floccosum. The vast majority of infections start at the distal end of the nail. Proximal subungual infections are quite rare in people with normal immune systems.
Figure 68-8. Green nail with onycholysis secondary to Pseudomonas aeruginosa infection.
(Courtesy of the Fitzsimons Army Medical Center teaching files.)
29. What should patients expect when undergoing treatment of onychomycosis?
The cure rate is 60% to 80% (not 100%). Fingernails grow 3 mm per month with complete replacement in about 6 months. Toenails grow 1 mm per month with replacement in 12 to 18 months. Therefore, at the end of a 6- to 12-week treatment course, the nails will not appear completely normal, but there usually is some healthy nail proximally. Of additional reassurance to patients is the fact that terbinafine and itraconazole reach maximum concentrations in the nail plate after discontinuing the medication, and they are present in the nail up to 9 months after treatment. There is a high risk of recurrence for toenail involvement, which can be mitigated by daily topical antifungal powders, creams, lacquers, and sprays.
Table 68-3. Antifungal Medications for Treatment of Toenail Onychomycosis
| DRUG | BRAND NAME | DOSE |
|---|---|---|
| Itraconazole | Sporanox | Continuous: 200 mg qd for 12 weeks Pulse: 200 mg bid 1 week per month for 12 weeks |
| Terbinafine | Lamisil | Continuous: 250 mg qd for 12 weeks Pulse: 250 mg qd 1 week per q 3 months for 6–12 months |
| Fluconazole | Diflucan | 150–200 mg every week for 12 months or until nails clear |
Adapted from Zaias N, Rebell G: The successful treatment of Trichophyton rubrum nail bed (distal subungual) onychomycosis with intermittent pulse-dosed terbinafine, Arch Dermatol 140:691–695, 2004.
Wolverton S: Comprehensive dermatologic drug therapy, Philadelphia, 2001, WB Saunders.
30. What is “habit tic” disorder? How is it different from median nail dystrophy?
This is a common self-induced nail condition of the thumb characterized by horizontal parallel ridges in the nail plate induced by constant manipulation of the cuticle and proximal nail fold. A closely related idiopathic condition, median nail dystrophy, can be easily confused with the above. Median nail dystrophy is marked by a normal cuticle and an inverted fir tree appearance to the central nail plate.
32. What is an exostosis?
An exostosis is a common benign bony growth that occurs on the distal phalanx, usually of the great toe. It involves the bone first and secondarily the nail. Trauma is thought to play a role in its development, and it most commonly affects adolescent women. It presents as a slow-growing painful mass under the nail with frequent secondary infection (Fig. 68-9). Plain x-rays will easily delineate the pathology.
