MNT Nail Anatomy and Pathology 2 — Questions and Answers
Question 1: Which nail finding is most characteristic of psoriasis?
- Koilonychia (spoon nails)
- Pitting, onycholysis, and oil-drop discoloration (Correct answer)
- Ram's horn deformity
- Blue-gray lunula
Correct 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).
Question 2: The nail plate is primarily composed of:
- Collagen fibers
- Hard keratin (alpha-keratin) (Correct answer)
- Calcium hydroxyapatite
- Elastin and fibronectin
Correct 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.
Question 3: Melanonychia striata refers to:
- Horizontal white bands on the nail
- A brown or black longitudinal streak on the nail plate (Correct answer)
- Nail plate fragmentation
- Green discoloration from Pseudomonas
Correct 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.
Question 4: What percentage of nail plate growth occurs from the nail matrix?
- 20%
- 100% (Correct answer)
- 50%
- 75%
Correct 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.
Question 5: Paronychia is defined as:
- Separation of the nail from the nail bed
- Infection and inflammation of the nail folds surrounding the nail plate (Correct answer)
- Fungal infection of the nail plate
- Bruising under the nail
Correct 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).
Question 6: The average growth rate of a healthy toenail is approximately:
- 3–4 mm per month
- 1.5 mm per month (Correct answer)
- 5 mm per week
- 0.5 mm per month
Correct 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.
MNT Nail Anatomy and Pathology 2
Which nail finding is most characteristic of psoriasis?