An Approach to the Unknown Rash
Rashes: An Approach to the Unknown Rash
How to diagnosis a rash
- Accurately describe the rash (eg. macule or nodule, vesicle, or bulla)
- Quickly "profile" the rash to see if it fits any classic pattern by patient age, rash distribution, or presence of hypotension
- Apply an algorithm based on the rash type
Rash Descriptors
| Descriptor | Definition |
|---|---|
| Lesion | Single small diseased area |
| Rash | Eruption of skin; more than single lesion |
| Macule | Circumscribed area of change without elevation |
| Papule | Solid raised lesion <1 cm |
| Nodule | Solid raised ≥1 cm |
| Plaque | Circumscribed elevated confluence of papules ≥1 cm |
| Pustule | Circumscribed area containing pus |
| Vesicle | Circumscribed fluid-filled area <1 cm |
| Bulla | Circumscribed fluid-filled area ≥1 cm |
| Petechia | Small red/brown macule ≤1 cm that does not blanch |
Quick Profiling of Rash
Patient Age
0-5 years
- Meningococcemia
- Kawasaki disease
- Viral exanthema
> 65 years
- Pemphigus vulgaris
- Sepsis
- Menigococcemia
- Toxic epidermal necrolysis
- Stevens Johnson syndrome
- Toxic shock syndrome
Rash
Diffuse Erythema
- Staph scalded skin syndrome
- Staph/strep toxic shock syndrome
- Necrotizing fasciitis
Mucosal Lesions
- Erythema ultiforme major
- Toxic epidermal necrolysis/Stevens Johnson syndrome
- Pemphigus vulgaris
Petechiae/Purpura
- Menigococcemia
- Necrotizing fasciitis
- Vasculitis
- Disseminated intravascular coagulopathy
- Rocky Mountain Spotted Fever
Symptoms
Hypotension
- Meningococcemia
- Toxic shock syndrome
- Rocky Mountain Spotted Fever
- Toxic epidermal necrolysis
- Stevens Johnson syndrome
Erythematous Rash
Maculopapular Rash
Petechial/ Purpuric Rash
Vesiculobullous Rash
References
- Murphy-Lavoie H, Le Gros TL. Emergent Diagnosis of the Unknown Rash. Emergency Medicine. 2010 March. PDF: [Source]
