Approach to the Hideous Whole Body Rash
Many past paper SAQs have asked the candidates to identify some rash, pupuric blotching, gangrenous embolic phenomena or some other visually impressive manifestation of disease. Irritatingly, the college examiners tend to remove these images from their published papers, presumably because they plan to reuse them. Previous questions of this sort have included Question 25.1 from the first paper of 2011 (erythema multiforme), Question 20.2 from the second paper of 2008 (Stevens-Johnson syndrome) and Question 10 from the first paper of 2005 (Toxic Epidermal Necrolysis). Question 15.1 from the second paper of 2012 was more about the non-specific approach to the evaluation of a gross whole-body rash. This approach is discussed below.
Generic list of differentials for a whole-body rash
- Shower of emboli
- Vascular insufficiency
- Toxic epidermal necrolysis
- Staphylococcal scalded skin syndrome
- Viral exanthem/manifestations of viral infection
- Fungal infection eg. candida
- Cutaneous lymphoma/leukaemia
- Stevens Johnson syndrome
- Red Man syndrome (vancomycin)
- Allergic reaction
- Erythema multiforme
- Graft-versus-host disease
Diagnostic work-up of a rash
- FBC for eosinophilia
- Viral serology for HSV, VZV, HIV, EBC, CMV
- Culture of exudate
- Mycoplasma serology
- Vasculitic screen
- Skin biopsy
This was the subject of Question 25.1 from the first paper of 2011.
- "target lesions"
- Mucous membrane involvement, especially oral mucosa
- Approximately 50% of cases are associated with herpes simplex.
- Mycoplasma pneumoniae
- Fungal infections eg. candida
Drugs which cause erythema multiforme:
Toxic epidermal necrolysis
Stevens-Johnson Syndrome and TEN are considered diseases of the same spectrum. SJS is the less severe classification of the same disease: only ~ 10% of the skin surface is sloughed. TEN, on the other hand, is a condition of over 30% slough. In the 10-30% patients, the two conditions overlap.
Thus, the diagnostic features:
- History of exposure to a new drug
- 1-3 weeks of waiting
- Fever and flu-like symptoms for 1-3 days before skin eruption
- Skin eruption: poorly defined macules with purpuric centres
- Then, blisters and epidermal detachment
- Symmetrical, primarily over face and upper trunk
- Complications similar to burns
- Mucosal involvement in 90%
- BOOP and respiratory mucosal sloughing can also occur
Drugs which are known to cause TEN:
I found this originally on the LITFL facebook page. It immediately struck me as a work of genius.