Condition	Characteristics
Acral melanoma	Black or brown pigmentation extending from the nail bed to the proximal or lateral nail folds (Hutchinson nail sign), pigmented stripe tapers distally; may cause knicking of the distal nail plate
Melanonychia striata	Band of black or brown pigmentation due to melanin beneath the nail plate; band is of uniform width; common in persons with dark skin complexion
Nail matrix hematoma	Large, acute hematomas that may cause tenderness from increasing nail bed pressure
Pseudomonas aeruginosa infection	Green discoloration usually involving the entire nail bed and multiple nails; diagnosis confirmed with fingernail culture
Subungual verruca vulgaris	Hyperkeratotic, rough papules with an irregular surface beneath the nail plate, causing nail plate deformation; may have a reddish or brown punctate appearance from capillary loop thrombosis