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Skin differentials – subungual haematoma vs subungual melanoma

The latest in GP and hospital practitioner Dr Andy Jordan's series on differentiating two often similar-looking skin conditions

Subungual haematoma and subungual melanoma cause pigmentation under the nail, but obviously their prognosis and management are markedly different.

Subungual haematoma

• Relatively common

• May be painful

• Usually affects nail of the big toe and may affect multiple nails, often with bilateral hallux involvement – from ill-fitting footwear

• Usually the haematoma is distal to the proximal nail fold and has a sharply demarcated curved proximal limit – the lateral margins are often wavy and divergent

• Associated subungual haemorrhages may occur in adjacent nails

• To confirm that the haematoma is growing out, a transverse groove in the nail can be scored at the proximal margin of the pigment and then observed over a few weeks

• Surgical exploration is indicated if pigment continues to spread proximally

• Subungual haematoma needs no treatment and the patient should be reassured that it is not a melanoma.

Subungual melanoma

• Rare, usually asymptomatic and affects thumb or big toe – only one nail is involved

• Tends to occur in middle-aged or elderly people

• Pigmentation also on the tip of the finger is characteristic of melanoma, as is pigmentation of the nail fold – Hutchinson's sign

• If there is associated nail damage without history of significant trauma, it is very likely to be due to melanoma

• Often presents as a new linear pigmented band along the length of the nail, which starts to widen progressively and becomes funnel shaped with the widest end proximally

• Some 30% of subungual melanomas are amelanotic or produce very little pigment, and the presentation is of progressive nail destruction or fissuring

• Tends to bleed easily

• Dermoscopy can help to make a diagnosis as subungual melanomas reveal a band of brown or black pigment comprising thin, irregular non-parallel lines

• Potentially lethal, and treatment involves incisional biopsy of matrix origin of pigmented band and then amputation of the digit.

Dr Andy Jordan is a GP and hospital practitioner in dermatology in Chesham, Buckinghamshire

Subungual haematoma is relatively common Subungual haematoma Subungual melanoma is rare Subungual melanoma