Synopsis
Read nail morphology as a diagnostic clue without overclaiming specificity, recognise melanoma and infection warnings, and connect psoriasis, clubbing, koilonychia and other changes to proportionate investigation.
- Nails record matrix, bed and systemic events slowly; name the structure and pattern before assigning a disease, because most single signs are not specific.
- Psoriasis causes regular pitting, oil-drop or salmon patches, subungual hyperkeratosis and onycholysis with an erythematous border, and may exist without obvious skin plaques.
- A new evolving irregular longitudinal melanonychia band in one adult nail, especially with periungual Hutchinson pigment or nail destruction, must be assessed urgently for melanoma.
- Longitudinal pigmentation across several nails can be physiological in darker skin or drug related, but change, symptoms and one-nail asymmetry remain important in every skin tone.
- True clubbing includes loss of the nail-fold angle, increased fluctuation and bulbous distal phalanx; it triggers cardiopulmonary, gastrointestinal and inflammatory assessment rather than a cosmetic referral.
- Koilonychia can accompany iron deficiency, while Beau lines mark temporary matrix arrest after severe illness or stress; neither establishes the systemic diagnosis by itself.
- Splinter haemorrhages are commonly traumatic and distal, but multiple proximal lesions plus fever, murmur or embolic features require urgent endocarditis assessment.
- Onycholysis occurs with psoriasis, fungus, trauma, thyroid disease and medicines; clip, examine and sample rather than inferring cause from separation alone.
- Nail-matrix biopsy can permanently alter growth and should be planned by a specialist who can target the lesion and orient histology correctly.
Key red flags
A new or changing single-nail longitudinal pigmented band with irregular width or colour, proximal widening, Hutchinson sign, nail dystrophy, bleeding, ulceration or a subungual mass requires urgent suspected melanoma assessment.
A new single band with irregular lines, colour variation, proximal widening, periungual extension or dystrophy raises nail-unit melanoma concern.
Thin longitudinal red-brown lines are often distal and traumatic; multiple proximal lesions with fever or embolic features raise endocarditis concern.
Investigation priorities
Define number, symmetry, anatomical structure and associated skin or joint phenotype.
Management branches
Longitudinal brown or black pigment appears in one or more nails.
- Ask onset, change, trauma, medicines, pregnancy, family pigmentation and melanoma history, then examine every nail, skin and mucosa and photograph with consent.
- Refer urgently a new or changing irregular single band, proximal widening, Hutchinson sign, dystrophy, bleeding or mass through the suspected melanoma pathway.
- For a genuinely low-risk stable pattern, specialist-led dermoscopic surveillance uses calibrated images and a defined interval; any evolution converts to biopsy assessment.