Defining Skin Lesions

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Contents

Introduction
Terminology
Types of rash
History
References
Related Articles

Introduction

Describing and defining skin lesions is a complicated business, and something that most doctors are not very good at!

There are a wide variety of terms used to describe skin lesions. In the days of smartphones, and quickly being able to send a picture to a colleague for assessment of a rash, this is perhaps less important than it used to be, but it is still useful to know some of the more common terms.

I find it helps to understand not only what the term describes, but the process that is giving rise to this type of rash, and I have summarised some of the terms below.

Terminology

Term	Description	Process
Macule	Flat Often red (not always) <1cm diameter Well defined border	Arises from the epidermis
Papule	Raised and palpable lesion <5mm diameter Well defined border Typically not compressible	Arises from the dermis
Patch	A larger macula	Arises from the epidermis
Maculopapular	Describes a combination of Macauley’s and Papuans
Nodule	A papule >5mm diameter	Arises from he epidermis
Plaque	A palpable lesion with a flat top >1cm diameter Well defined border Not compressible
Wheal	Raised Blanches Compressible	Caused by oedema of the dermis
Vesicle	A fluid filled lesion <5mm diameter Raised	Arises from the epidermis
Bulla	A vesicles >5mm diameter
Pustule	Visible collection of pus in the skin <10mm diameter
Abcess	A pustule >10mm diameter
Purpura	Bleeding into the dermis Multiple dark coloured spots – can be red or purple in colour Can be macular or papular
Petechiae	Purpura <2mm diameter
Haematoma	Swelling from a large bleed in the skin Often tender and palpable
Erythema	“Redness”	Increased vascularise – often due to an inflammatory process
Milia	Tiny white spots	Contain keratin, occurs as a result of blocked pilosebacious glands
Papilloma	Warty-like appearance Tiny ‘finger-like’ projections from the skin surface	Typically from wart viruses (HPV viruses)
Ulcer	A deep skin defect	Goes all the way through the epidermis and may or may not effect the dermis Erosion and Ulcer
Erosion	A shallow skin defect	Effects the epidermis only
Fissure	A split in the skin	Effects dermis and epidermis
Excoriation	Scratch marks
Keloid	Scar tissue that goes beyond the boundaries of the original injury

Types of rash

It may also help to try and split dermatological diagnoses into 7 types, as per Professor Robin Marks:

Infection
- Bacterial
  - Impetigo
  - Cellulitis
- Viral
  - Herpes simplex
  - Chicken pox
  - Warts
  - Pityriasis rosea
  - Viral rash – “viral exanthem”
- Fungal
  - Tinea
  - Candidiasis
  - Pityriasis Versicolor
Acne
Psoriasis
Eczema
Urticaria
Sun-related skin cancers
Drug-related eruptions

History

Location and timing

Where is the rash?
When did it start?

Itch

Is it itchy?

Drugs

Have you taken any medication recently?
[Has the appearance of the rash been changed by treatment?]

Contacts

Does anybody you know have a similar rash?

Other

Have you got a history of any rashes or anything similar?
Have you changed washing powder / soap / shower gel / skin products recently?
What do you do for work?

References

Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy