Hello, welcome to HCM. Nail plate pigmentation (melanonychia
) is a rather common clinical occurrence. Melanonychia striata, or longitudinal melanonychia (LM), is characterized as either a dark brown or brown-black longitudinal band on a toenail or fingernail. The three most common variants of LM are melanocytic nevus
, melanotic macule, and melanoma
in situ. There have been reports of melanocytic nevus and melanotic macules progressing to melanomas. You must visit a dermatologist
to get it evaluated. You may need a biopsy of it. Wish you good health.