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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

Macule and Patch

Papule
  • Raised and palpable lesion
  • <5mm diameter
  • Well defined border
  • Typically not compressible
  • Arises from the dermis

Papule and Plaque

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

Vesicle and Bulla

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 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‚Äôs 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

Read more about our sources

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