The presence of melanin in the soft tissues surrounding the nail.
The symptom is characteristic of subungual melanoma and may be visible on dermoscopy.
It can also occur in some other, rare diseases, such as: Laugier-Hunziker-Aries syndrome, Peutz-Jeghers syndrome, congenital signs of the nail apparatus, non-melanocytic nail tumors, regressive nevoid nail melanosis, as well as with certain drugs (e.g. minocycline) .
Lit.: [1] Sobjanek M., Włodarkiewicz A., Toboła J .: Melanonychia longitudinalis. Post Dermatol Alergol 2006, 23; 130-7.
Source: A. Kaszuba, Z. Adamski: “Lexicon of dermatology”; XNUMXst edition, Czelej Publishing House