Reviews

Evaluation of nail lines: Color and shape hold clues

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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.

 

References

Inspection of the fingernails and toenails should be part of a complete physical examination. A basic understanding of nail anatomy and recognition of several basic types of nail lines and bands allow the clinician to properly diagnose and treat the nail disease, to recognize possible underlying systemic diseases, and to know when to refer the patient to a dermatologist for specialized evaluation and biopsy.

In this review, we delineate the three basic types of nail lines­—white lines (leukonychia striata), brown-black lines (longitudinal melanonychia), and red lines (longitudinal erythronychia)—and the differential diagnosis for each type. We also discuss grooves in the nail plate, or Beau lines.

BASIC NAIL ANATOMY

A fundamental understanding of the anatomy of the nail unit is necessary to understand the origin of nail diseases and underlying pathologic conditions.

The nail unit includes the nail matrix, the lunula, the nail fold, the nail plate, and the nail bed. The nail matrix extends from under the proximal nail fold to the half-moon-shaped area (ie, the lunula) and is responsible for nail plate production. The nail bed lies under the nail plate and on top of the distal phalanx and extends from the lunula to just proximal to the free edge of the nail; its rich blood supply gives it its reddish color.

Nails grow slowly, and this should be kept in mind during the examination. Regrowth of a fingernail takes at least 6 months, and regrowth of a toenail may take 12 to 18 months. Therefore, a defect in the nail plate may reveal an injury that occurred—or a condition that began—several months before.1

NAIL EXAMINATION ESSENTIALS

A complete examination includes all 20 nail units and the periungual skin. Patients should be instructed to remove nail polish from all nails, as it may camouflage dystrophy or disease of the nail. Photography and careful measurement help document changes over time.

LEUKONYCHIA STRIATA: WHITE NAIL LINES

White nail lines or leukonychia is classified as true or apparent, depending on whether the origin is in the nail matrix or the nail bed.

In true leukonychia, there is abnormal keratinization of the underlying nail matrix, resulting in parakeratosis within the nail plate and an opaque appearance on examination.2 The white discoloration is unaffected by pressure, and the opacity moves distally as the nail grows out, which can be documented by serial photography on subsequent visits.

Apparent leukonychia involves abnormal nail bed vasculature, which changes the translucency of the nail plate. The whiteness disappears with pressure, is unaffected by nail growth, and will likely show no change on later visits with serial photography.3

True leukonychia

Leukonychia striata, a subtype of true leuko­nychia, is characterized by transverse or longitudinal bands. It is most often associated with microtrauma, such as from a manicure.4 Lines due to trauma are typically more apparent in the central part of the nail plate; they spare the lateral portion and lie parallel to the edge of the proximal nail fold.5

Figure 1. Onychomycosis of the great toenail result-ing in a dermatophytoma, visible as a white-yellow longitudinal band.

Onychomycosis. White longitudinal bands may also be seen in onychomycosis, a fungal infection of the nail accounting for up to 50% of all cases of nail disease. The infection may present as irregular dense longitudinal white or yellowish bands or “spikes” on the nail plate with associated hyperkeratosis, known as a dermatophytoma (Figure 1).

If a fungal infection is suspected, a potassium hydroxide stain can be performed on the subungual debris, which is then examined with direct microscopy.6 Alternatively, the physician can send a nail plate clipping in a 10% buffered formalin container with a request for a fungal stain such as periodic acid-Schiff.7 Microscopic examination of a dermatophytoma shows a dense mass of dermatophyte hyphae, otherwise known as a fungal abscess.8

The physician can play an important role in diagnosis because clinical findings suggestive of a dermatophytoma are associated with a poor response to antifungal therapy.9

Inherited diseases. White longitudinal bands are also an important clue to the rare autosomal dominant genodermatoses Hailey-Hailey disease (from mutations of the ATP2A2 gene) and Darier disease (from mutations of the ATP2C1 gene). Patients with Hailey-Hailey disease may have nails with multiple parallel longitudinal white stripes of variable width originating in the lunula and most prominent on the thumbs.10–12 These patients also have recurrent vesicular eruptions in flexural skin areas, such as the groin, axilla, neck, and periumbilical area causing significant morbidity.

Patients with Darier disease may have nails with alternating red and white longitudinal streaks, described as “candy-cane,”13 as well as wedge-shaped distal subungual keratosis accompanied by flat keratotic papules on the proximal nail fold.14 These nail changes are reported in 92% to 95% of patients with Darier disease.15,16 Patients typically have skin findings characterized by keratotic papules and plaques predominantly in seborrheic areas and palmoplantar pits, as well as secondary infections and malodor causing significant morbidity.15 Therefore, knowing the characteristic nail findings in these diseases may lead to more rapid diagnosis and treatment.

Mees lines. Leukonychia striata can present as transverse white lines, commonly known as Mees lines. They are 1- to 2-mm wide horizontal parallel white bands that span the width of the nail plate, usually affecting all fingernails.17 They are not a common finding and are most often associated with arsenic poisoning. They can also be used to identify the time of poisoning, since they tend to appear 2 months after the initial insult.

Mees lines are also associated with acute systemic stresses, such as acute renal failure, heart failure, ulcerative colitis, breast cancer, infections such as measles and tuberculosis, and systemic lupus erythematosus, and with exposure to toxic metals such as thallium.3

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