Evaluation of nail lines: Color and shape hold clues
ABSTRACTNail lines are a common presenting finding. A thorough inspection of the fingernails and toenails is an integral part of the complete physical examination. An understanding of basic nail anatomy and familiarity with several basic types of nail line enable the clinician to diagnose and treat nail disorders and to recognize underlying systemic diseases, as each type of nail line has a particular differential diagnosis. The authors review leukonychia striata (white lines), longitudinal melanonychia (brown-black lines), longitudinal erythronychia (red lines), and nail-plate grooves (Beau lines).
KEY POINTS
- Transverse white nail lines, or Mees lines, have been associated with acute systemic stress, such as from acute renal failure, heart failure, ulcerative colitis, breast cancer, infection (measles, tuberculosis), and systemic lupus erythematosus, and with exposure to toxic metals such as thallium.
- In true leukonychia, there is abnormal keratinization of the underlying nail matrix, resulting in a white discoloration that is unaffected by pressure. In apparent leukonychia, the white discoloration is due to abnormal nail bed vasculature, and the whiteness disappears with pressure.
- Brown-black nail lines may represent blood from trauma; bacterial, fungal, or viral infection; drug reaction; endocrine disorders; exogenous pigmentation; excess melanin production within the nail matrix; nevi; or melanoma.
LONGITUDINAL ERYTHRONYCHIA: VERTICAL RED NAIL LINES
Longitudinal erythronychia—the presence of one or more linear red bands in the nail unit—can be localized (involving only one nail) or polydactylous (involving more than one nail). The localized form is usually due to a neoplastic process, whereas involvement of more than one nail may indicate an underlying regional or systemic disease.13 Table 2 lists indications for referral to a nail specialist.
General features on examination
Clinical examination reveals one or more linear, pink-red streaks extending from the proximal nail fold to the distal free edge of the nail plate (Figure 4). The width of the band typically ranges from less than 1 mm to 3 mm.40 Other features may include splinter hemorrhages within a red band, a semitransparent distal matrix, distal V-shaped chipping, splitting, onycholysis of the nail plate, and reactive distal nail bed and hyponychial hyperkeratosis. These features can be visible to the naked eye but may be better viewed with a magnifying glass, a 7× loupe, or a dermatoscope.13
Localized longitudinal erythronychia is usually seen in middle-aged individuals and is most commonly found on the thumbnail, followed by the index finger.41,42 The condition may be asymptomatic, but the patient may present with pain or with concern that the split end of the nail catches on fabrics or small objects.42
Glomus tumor
Intense, pulsatile pain with sensitivity to cold and tenderness to palpation is highly suggestive of glomus tumor,43 a benign neoplasm that originates from a neuromyoarterial glomus body. Glomus bodies are located throughout the body but are more highly concentrated in the fingertips, especially beneath the nails, and they regulate skin circulation. Therefore, the nail unit is the most common site for glomus tumor.44,45 A characteristic feature of subungual glomus tumor is demonstration of tenderness after pin-point palpation of the suspected tumor (positive Love sign).45 While it is typical for glomus tumor to affect only one nail, multiple tumors are associated with neurofibromatosis type 1.46 Confirmation of this diagnosis requires referral to a dermatologist.
Other causes of localized red nail lines
Onychopapilloma, a benign idiopathic tumor, is the most common cause of localized longitudinal erythronychia. Unlike glomus tumor, it is usually asymptomatic.42,47 Less common benign conditions are warts, warty dyskeratoma, benign vascular proliferation, a solitary lesion of lichen planus, hemiplegia, and postsurgical scarring of the nail matrix. In some cases, the lines are idiopathic.42,43
Malignant diseases that can present as localized longitudinal erythronychia include invasive squamous cell carcinoma, squamous cell carcinoma in situ (Bowen disease), and, less frequently, amelanotic melanoma in situ, malignant melanoma, and basal cell carcinoma.42 Squamous cell carcinoma in situ most commonly presents in the 5th decade of life and is the malignancy most commonly associated with localized longitudinal erythronychia. Clinically, there is also often nail dystrophy, such as distal subungual keratosis or onycholysis.43
Patients with asymptomatic, stable localized longitudinal erythronychia may be followed closely with photography and measurements. However, any new lesion or a change in an existing lesion should prompt referral to a dermatologist for biopsy.13
Red streaks on more than one nail
Polydactylous longitudinal erythronychia usually presents in adults as red streaks on multiple nails and, depending on the presence or absence of symptoms (eg, pain, splitting), may be the patient’s chief complaint or an incidental finding noted by the astute clinician. Often, it is associated with systemic disease, most commonly lichen planus or Darier disease.
Lichen planus is a papulosquamous skin disease with nail involvement in 10% of patients and permanent nail dystrophy in 4%. Common nail findings include thinning, longitudinal ridging, and fissuring, as well as scarring of the nail matrix resulting in pterygium. Linear red streaks may accompany these more typical nail findings.13 Patients with Darier disease present with alternating red and white linear bands on multiple nails as in leukonychia striata.
Less frequently, polydactylous longitudinal erythronychia is associated with primary and systemic amyloidosis, hemiplegia, graft-vs-host disease, acantholytic epidermolysis bullosa, acantholytic dyskeratotic epidermal nevus, acrokeratosis verruciformis of Hopf, or pseudobulbar syndrome, or is idiopathic.13,42,48 Therefore, the physician evaluating a patient with these nail findings should focus on a workup for regional or systemic disease or refer the patient to a dermatologist who specializes in nails.
BEAU LINES
Beau lines are a common finding in clinical practice. They are not true lines, but transverse grooves in the nail plate that arise from the temporary suppression of nail growth within the nail matrix that can occur during periods of acute or chronic stress or systemic illness (Figure 5).49
The precipitating event may be local trauma or paronychia, chemotherapeutic agents cytotoxic to the nail matrix, or the abrupt onset of systemic disease.18,50 The grooves have also been associated with rheumatic fever, malaria, pemphigus, Raynaud disease, and myocardial infarction, as well as following deep-sea dives.51–53 The distance of a Beau line from the proximal nail fold can provide an estimate of the time of the acute stress, based on an average growth rate of 3 mm per month for fingernails and 1 mm per month for toenails.49
