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A 28-year-old man is in the office for a work physical and asks about the white streaks on his fingernail (Figure 190-1). He has had them on and off all of his adult life, but recently developed more of them and was concerned he may have a vitamin deficiency. He was reassured that this is a normal nail finding often associated with minor trauma.

Figure 190-1

Transverse striate leukonychia (transverse white streaks) in a healthy patient. Note that the lines do not extend all of the way to the lateral folds, which indicates a probable benign process. (Courtesy of Richard P. Usatine, MD.)

The anatomy of the nail unit is shown in Figure 190-2. The nail unit includes the nail matrix, nail plate, nail bed, cuticle, proximal and lateral folds, and fibrocollagenous supportive tissues. The proximal matrix produces the superficial aspects of the plate, and the distal matrix the deeper portions. The nail plate is composed of hard and soft keratins, is formed via onychokeratinization, which is similar to hair sheath keratinization.1 Most normal nail variants occur as a result of accentuation or disruption of normal nail formation.

Figure 190-2

The anatomy of the nail unit. (Courtesy of Usatine R, Pfenninger J, Stulberg D, Small R. Dermatologic and Cosmetic Procedures in Office Practice. Elsevier, Inc., Philadelphia. 2012.)

  • Leukonychia.
    • Transverse striate leukonychia.
    • Leukonychia punctata.
    • White nails.
  • Longitudinal melanonychia (LM).
    • Racial melanonychia in African Americans.
  • Nail hypertrophy and onychogryphosis (also known as onychogryposis).
    • Ram's horn nail.
    • Oyster-like deformity.
    • Lateral nail hypertrophy.
    • Thickened toenail.

Melanonychia often involves several nails and is a more common occurrence in those patients with darker skin types. Among African Americans, benign melanonychia affects up to 77% of young adults and nearly 100% of those age 50 years or older. In the Japanese, LM affects 10% to 20% of adults.1 Nail matrix nevi have been reported to represent approximately 12% of LM in adults and 48% in children.2 The incidences of most other benign nail findings are not well established.

  • Leukonychia represents benign, single or multiple, white spots or lines in the nails. Patchy patterns of partial, transverse white streaks (transverse striate leukonychia, see Figure 190-1) or spots (leukonychia punctata, Figure 190-3) are the most common patterns of leukonychia.3 Leukonychia is common in children and becomes less frequent with age. Parents may fear that it represents a dietary deficiency, in particular a lack of calcium, but this concern is almost always unfounded.
  • Most commonly, no specific cause for leukonychia can be found. It is usually the result of minor trauma to the nail cuticle or matrix and is the most commonly found nail condition in children.4 When the lesions are caused by overly aggressive manicuring ...

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