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Clinical Quiz: Black nail

A woman asks if she can buy something to make her big toe nail "look better". You ask to see, and she shows you a blackened nail. She says she can't remember for how long the nail has looked black, and doesn't remember injuring her toe recently.QUESTIONS

1. Black toe nails such as this are always caused by harmless bruising. True or false?

2. Bruises will usually grow out over a few days, and the patient should be advised to check that this happens. True or false?

3. If underlying malignancy is suspected a biopsy will allow a definitive answer. True or false?

4. Once a sinister cause has been ruled out, the patient can be advised to apply coloured nail varnish to improve the appearance of the nail. True or false?

5. Other causes of discoloured nails include fungal infections. True or false?


1. False. In most cases this type of appearance is the result of bruising. However, rarely it can be the result of a subungal malignant melanoma, which can potentially be fatal.

2. False. Toe nails grow very slowly and it can take up to 12 months for a haematoma to disappear.

3. True. Either complete removal of the nail and a biopsy of the nail bed, or occasionally a biopsy from the base of the nail, will give a definitive diagnosis.

4. True. Coloured nail varnish is a good way to hide the bruising.

5. True. Onychomycosis can cause not only discolouration of the nail but also thickening and deformity. In these cases oral antifungals such as terbinafine are the best method of treatment, and patients should be referred to a GP.

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