Rash

Question 1

Differentials of Rash

Answer 1

1. Herpes zoster*
2. Urticaria*
3. ITP*
4. Allergic - contact or atopic dermatitis
5. Varicella
6. Measles
7. Rubella
8. Impetigo
9. Cancer - Leukemia, lymphoma
10. Scabies
11. Psoriasis
12. HSP
13. Meningococcemia
14. HIV
15. EBV

Question 2

Rash - Key points in history

Answer 2

• Should be adapted to patient’s age as viral exanthema common in children.
• Site and mode of onset of rash, mode of progression and past history (e.g. eczema).
• Constitutional disturbance (e.g. pyrexia, pruritus).
• Drug history and exposure to irritants.
• Diet including unaccustomed food.
• Herald patch (pityriasis rosea).
• Contact with infectious diseases including child carecentres and school.
• Overseas travel.
• Bleeding or bruising tendency.

Question 3

Rash - Key points in PE

Answer 3

Skin of whole body
•Nature and distribution of the rash including lesion characteristics
•Nails and soles of feet
•Scalp, mucous membranes and oropharynx
•Conjunctivae and the lymphopoietic system (?lymphadenopathy, ?splenomegaly)

Question 4

Rash - Key investigations

Answer 4

Many diagnoses are clinical. 
Consider:
•FBE/ESR/CRP
•EBV test
•HIV test
•serology for rubella, parvovirus, syphilis and other suspected infections
•viral and bacterial cultures.

Question 5

Rash - Diagnostic tip

Answer 5

Be vigilant for the deadly meningococcal septicaemia, which may present as an erythematous rash initially prior to the development of purpura.
•Prescribed drugs are a common cause of rash, especially toxic erythema. 
Examples are 
1. antibiotics, especially penicillin, 
2. thiazides, 
3. anti-epileptics, 
4. allopurinol, 
5. NSAIDs and other 
6. anti-arthritic agents