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
