Dermatology Case Studies

ABCDE Rule

Clinical Assessment of a Lesion

They have attached a photograph of their thumb:

Discolouration under nail

Figure 11: Discolouration under thumb nail

You assess this photograph according to the ABCDE criteria, a very useful system for examining most skin lesions
You might have to modify your approach a little in this case
It is important to note that this photograph appears to show a bruise trapped beneath the nail, which fades slightly at the top
It is also noteworthy that the bruising extends right down to the nail bed, this is a reassuring feature in a traumatic nail injury

Click each of letters of the mnemonic to reveal the assessment:

A is for Asymmetry

In this case the shape of the lesion will appear consistent with bruising, with blood trapped beneath the nail

B is for Border irregularity

In this case the shape of the lesion will appear consistent with bruising, with blood trapped beneath the nail
A very important point of history is to consider the border of the haematoma
In this case it extends down to the nail bed which would be consistent with the effect of gravity on blood pooling beneath a nail and is a reassuring feature in this case

C is for Colour variability and/or Changing colour

In the case of a subungual haematoma you would expect the colour to change, lighten, reduce and eventually disappear as the bruise resolves
If it has not significantly reduced or seemed to increase over the course of the next few weeks, it will need to be reassessed
It's very important that the patient is made aware of that fact

D is for Different

The history and appearances in this scenario are typical of an injury to a digit causing a subungual haematoma
You should be alert to any situations where you are asked to assess images of nail changes which differ from this situation

E is for Evolving (changing)

A subungual haematoma will usually resolve and recede and will demonstrate similar colour changes to a bruise elsewhere in the body
The patient should be made aware of this and told to report and changes that are inconsistent with this process

ABCDE criteria info from https://dermnetnz.org/topics/abcdes-of-melanoma