Tagg, A. Paediatric dermatology, Don't Forget the Bubbles, 2020. Available at:
Whether it is the primary complaint or a symptom of the underlying disease many children present to health care practitioners with skin conditions.
The Skin Deep Project is a collection of photographs and descriptions of paediatric skin lesions led by Don’t Forget The Bubbles and the Royal London Hospital with contributors from all over the world. The project focuses on providing high quality, accessible images which improve the diversity available in paediatric skin images found online. This will improve identification and patient care.
But first in order to help identify skin lesions it is helpful to know the right terms to use. So let’s start there…
Basic skin anatomy
The skin is made up of three layers: the epidermis. the dermis and a layer of subcutaneous fat. The epidermis is made of many layers of epithelial cells. Near the bottom of the epidermis are melanocytes. These are a special type of cell that produces melanin, a dark pigment responsible for giving skin it’s colour. The dermis is made up of connective tissue and contains hair follicles, sweat glands, sebaceous glands, branches of blood vessels, and nerve endings. The subcutaneous fat layer below the dermis helps to give our bodies protection, regulate temperature, and anchor the dermis to structures below such as muscle or bone. It also contains blood vessels.
Skin forms a protective barrier for the body but also has multiple other functions including immunological protection, temperature regulation, synthesis of vitamin D, sensation, secretion, and excretion.
Whilst history is very important, paediatric dermatology is often truly down to the spot diagnosis. It would be great if we could just send pictures straight to the electronic medical record but this is not always possible.
Some rashes are easily diagnosed by their location – why do you think it is called Hand, Foot and Mouth? These are LOCALIZED rashes. Are they in a DERMATOMAL distribution, like in shingles or in a sun-exposed area. PHOTOSENSITIVE ares. Others are harder to place and are more GENERALIZED in their location.
The skin changes associated with eczema are more commonly seen on FLEXURAL surfaces (i.e. the creases) whereas the plaques of psoriasis are more likely to be found on EXTENSOR surfaces.
Having figured out the distribution of the lesion it is then time to figure out the configuration. This is the pattern or shape.
Are the lesions DISCRETE (separate) or CONFLUENT (joined together)? Are they LINEAR or not? Are the TARGET lesions, ANNULAR, or DISCOID?
Primary skin lesions
Skin lesions can be primary or secondary. Primary lesions arise directly from a disease process/cause. Secondary lesions progress from a primary lesion or due to transformation from interacting with the environment (eg. heat, chemicals) or a patient’s actions (eg. picking, rubbing) .
Primary skin lesions include:
CRUST: The skin is covered in a layer of dried matter – usually serum, blood, pus, or a combination of these.
CYST: A closed cavity, filled with semi-solid or liquid material such as fluid or blood. It can be lined with epithelium or endothelium. A Cyst which is filled with pus is a PUSTULE.
MACULE: A small, flat, non-palpable skin lesion that is less than 1 cm diametre in size. Note that this type of lesion which is >1cm is usually referred to as a PATCH.
PUSTULE: A pus filled elevated skin lesion, often with surrounding erythema.
ULCER: A defect in the skin or mucous membranes (loss of epidermis +/- deeper layers. They are deep and often leave a scar when they heal
VESICLE: A well rounded, raised, fluid filled lesion which is <1cm in dimaetre (a BULLA is >1cm in size)
WHEAL/HIVE: A pink, oedematous papule from swelling in the dermis that can vary in size and shape. They are usually erythematous but can have a paler centre.
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