Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, September 2016.
Nails are generally a pinkish colour. A white nail describes the appearance of one or more fingernails and/or toenails that are partially or completely white in colour. This appearance is also called leukonychia.
Total leukonychia is a whitening of the entire nail plate.
Partial leukonychia has 3 subtypes:
Muehrcke lines are a form of transverse apparent leukonychia due to variable blood flow under the nail; pressure on the nail plate makes them disappear. Vitiligo or leukoderma (white skin) can also cause apparent partial or longitudinal leukonychia.
White nails can affect anyone: males and females of any age or ethnicity.
The nail plate can be damaged in part or whole by injury to the nail plate or the matrix (growth area at the base of the nail). Disruption of the horizontal layers of keratin, with air trapping, results in reflection and lack of transparency.
Types of injury causing punctate leukonychia include nail biting, manicuring, knocks and bangs, and tight footwear. The white spots grow out as the nail grows (about 6 to 9 months for a fingernail). Striate leukonychia may follow damage to the nail matrix, and furrows and ridges may also appear in the. Total leukonychia can be follow a more serious injury, often with detachment of the nail plate from the nail bed, and alteration to the nail contour.
White nails can be due to:
Terry nails have been associated with:
Leukonychia should be distinguished from onycholysis, in which the nail plate appears white or yellowish because it has been lifted away from its underlying nail bed.
If the cause of leukonychia is not clear, the following tests may be helpful.
Treatment depends on the underlying cause of leukonychia.
Leukonychia due to minor trauma or medication may completely resolve over a few months, In other cases, the white nail plate remains long term, or become recurrent.
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