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Evaluation of nail lines: Color and shape hold clues

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Apparent leukonychia

Apparent leukonychia can alert the physician to systemic diseases, infections, drug side effects, and nutrient deficiencies. Specific nail findings include Muehrcke lines, “half-and-half” nails, and Terry nails.

Muehrcke lines are paired white transverse bands that span the width of the nail bed and run parallel to the distal lunula. They were first described in the fingernails of patients with severe hypoalbuminemia, some of whom also had nephrotic syndrome, which resolved with normalization of the serum albumin level. Muehrcke lines have since been reported in patients with liver disease, malnutrition, chemotherapy, organ transplant, human immunodeficiency virus (HIV) infection, and acquired immunodeficiency syndrome.3,18 They are associated with periods of metabolic stress, ie, when the body’s capacity to synthesize proteins is diminished.19

Figure 2. “Half-and-half” nails involve a transverse white band proximally and a red-brown band distally. Underlying conditions include Kawasaki disease, cirrhosis, Crohn disease, and zinc deficiency.

Half-and-half nails, or Lindsay nails, are characterized by a white band proximally, a pink or red-brown band distally, and a sharp demarcation between the two (Figure 2). They were originally described in association with chronic renal disease,20 and surprisingly, they resolve with kidney transplant but not with hemodialysis treatment or improvement in hemoglobin or albumin levels.21–23 Half-and-half nails have been reported with Kawasaki disease, hepatic cirrhosis, Crohn disease, zinc deficiency, chemotherapy, Behçet disease, and pellagra.3,24,25 They should be distinguished from Terry nails, which are characterized by leukonychia involving more than 80% of the total nail length.26

Terry nails were originally reported in association with hepatic cirrhosis, usually secondary to alcoholism27 but have since been found with heart failure, type 2 diabetes mellitus, pulmonary tuberculosis, reactive arthritis, older age, Hansen disease, and peripheral vascular disease.3,26,28,29

LONGITUDINAL MELANONYCHIA: VERTICAL BROWN-BLACK NAIL LINES

Figure 3. Longitudinal melanonychia presents as one or more longitudinal brown-black bands in the nail plate. Underlying conditions include melanoma in situ (A) and benign nevus (B).

Longitudinal melanonychia is the presence of black-brown vertical lines in the nail plate. They have a variety of causes, including blood from trauma; bacterial, fungal, or HIV infection; drug therapy (eg, from minocycline); endocrine disorders (Addison disease); exogenous pigmentation; or excess melanin production within the nail matrix.30–32 They may also be a sign of a benign condition such as benign melanocytic activation, lentigines, or nevi, or a malignant condition such as melanoma (Figure 3).33,34

When to suspect melanoma and refer

Although melanoma is less commonly associated with brown-black vertical nail lines, awareness of melanoma-associated longitudinal melanonychia reduces the likelihood of delayed diagnosis and improves patient outcomes.35 Also, it is important to remember that although nail melanoma is more common in the 5th and 6th decades of life, it can occur at any age, even in children.36

Findings that raise suspicion of nail melanoma (Table 1)33,37 and that should prompt referral to a dermatologist who specializes in nails include the following:

  • A personal or family history of melanoma
  • Involvement of a “high-risk” digit (thumb, index finger, great toe),30,31,38 although nail melanoma can occur in any digit
  • Any new vertical brown-black nail pigmentation in a fair-skinned patient
  • Only one nail affected: involvement of more than one nail is common in people with darker skin, and nearly all patients with darker skin exhibit longitudinal melanonychia by age 5031
  • Changes in the band such as darkening, widening, and bleeding
  • A bandwidth greater than 6 mm33
  • A band that is wider proximally than distally34
  • Nonuniform color of the line
  • Indistinct lateral borders
  • Associated with pigmentation of the nail fold (the Hutchinson sign, representing subungual melanoma),31,39 nail plate dystrophy, bleeding, or ulceration.33

While these features may help distinguish benign from malignant causes of longitudinal melanonychia, the clinical examination alone may not provide a definitive diagnosis. Delayed diagnosis of nail melanoma carries a high mortality rate; the internist can promote early diagnosis by recognizing the risk factors and clinical signs and referring the patient to a dermatologist for further evaluation with nail biopsy.

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