Nail Lab
9 small windows on skin and systemic disease. For each finding: what it looks like, and what it votes for.
Onychomycosis (tinea unguium)
Yellow-white discoloration starting at the free edge, subungual hyperkeratosis with crumbling, thickening and distal onycholysis; usually toenails, often with tinea pedis nearby.
Votes for
- Tinea pedis
- Diabetes and peripheral vascular disease
- Older age
- Immunosuppression
Pitting
Multiple small punctate depressions in the nail plate, like the surface of a thimble.
Votes for
- Psoriasis (the classic)
- Alopecia areata
- Eczema near the matrix
Onycholysis
Distal separation of the plate from its bed, the free edge turns white-yellow and lifts.
Votes for
- Psoriasis
- Onychomycosis
- Trauma
- Thyroid disease
Clubbing
Loss of the angle between fold and plate; bulbous fingertip; the facing-nails diamond window (Schamroth) disappears.
Votes for
- Chronic hypoxic lung disease and lung cancer
- Cyanotic heart disease
- Inflammatory bowel disease, cirrhosis
Koilonychia
Spoon-shaped, concave nails that could hold a water drop.
Votes for
- Iron-deficiency anaemia
- Normal finding in infants
Splinter haemorrhages
Thin longitudinal red-brown lines under the plate, like wood splinters.
Votes for
- Trauma (by far the most common)
- Infective endocarditis when multiple and proximal
- Psoriasis, vasculitis
Longitudinal melanonychia
A brown-black band running the length of the nail.
Votes for
- Benign ethnic melanonychia, common and often multiple in deeply pigmented skin
- Naevus of the matrix
- Subungual melanoma, worry when a SINGLE new band widens, darkens, blurs, or spills pigment onto the fold (Hutchinson sign)
Beau lines
Transverse grooves across the plate at the same level on multiple nails.
Votes for
- Severe systemic illness arresting nail growth
- Chemotherapy
- Date the insult: the groove migrates out at ~1 mm per 10 days
Oil-drop (salmon patch) sign
A translucent yellow-pink patch under the plate, like a drop of oil beneath glass.
Votes for
- Psoriasis, highly characteristic
The nail finding that must never be waved through: a single new longitudinal pigmented band that widens, darkens, or spills pigment onto the nail fold, subungual melanoma until proven otherwise, in every skin tone.