When to worry about discoloured nails and melanonychia

Discoloured Nails is a common presentation of Melanonychia. Melanonychia describes brown or black pigment appearing in the nail, often as a stripe that runs from the base toward the tip. It can affect one nail or several and may follow injury, repeated pressure, medication, or increased pigment production.

A broadening stripe, uneven shades, irregular edges, or pigment extending onto the cuticle or adjacent skin needs careful examination. These clues do not identify the cause on their own, but they help a clinician decide whether further assessment is needed.

Take a close photograph in natural light and note which nail is involved, when the mark began, and whether it is widening as the nail grows. Avoid filing away the surface or covering the nail with polish before review. A dermatologist can examine the pigment and compare it with the nail pattern on other fingers or toes.

If the appearance is unclear, the clinician may discuss monitoring, testing, or taking a sample. Follow the agreed review plan even if the nail is not painful.

Arrange prompt dermatology review for a new stripe, a mark that is widening or changing colour, pigment on the surrounding skin, nail splitting, bleeding, or a mass beneath the nail. Seek earlier advice when only one nail is affected and the change has no clear injury-related explanation.

Ask whether the pigment follows the nail growth pattern, whether the cuticle and nearby skin are involved, and what changes should trigger an earlier review. Mention trauma, medicines, family history, and any similar marks on other nails.