Nail Anatomy and Pathology Flashcards

Which nail finding is most characteristic of psoriasis?

Answer: Pitting, onycholysis, and oil-drop discoloration

Psoriatic nail disease commonly presents with nail pitting (from matrix involvement), onycholysis (nail bed plaques), and the 'oil-drop' sign (yellow-brown subungual discoloration).

The nail plate is primarily composed of:

Answer: Hard keratin (alpha-keratin)

The nail plate is composed of hard (alpha) keratin, a sulfur-rich protein that gives the nail its rigidity and protective function.

Melanonychia striata refers to:

Answer: A brown or black longitudinal streak on the nail plate

Melanonychia striata is a longitudinal brown-black streak resulting from melanocyte activation or proliferation within the nail matrix; it requires evaluation to exclude subungual melanoma.

What percentage of nail plate growth occurs from the nail matrix?

Answer: 100%

The nail plate is entirely produced by the nail matrix; the nail bed contributes subungual keratin but does not produce the plate itself.

Paronychia is defined as:

Answer: Infection and inflammation of the nail folds surrounding the nail plate

Paronychia is an infection of the periungual tissue (nail folds), which may be acute (bacterial, commonly Staphylococcus aureus) or chronic (often Candida-related).

The average growth rate of a healthy toenail is approximately:

Answer: 1.5 mm per month

Toenails grow approximately 1.5 mm per month (versus 3–4 mm for fingernails), meaning a full toenail replacement takes 12–18 months.