February 2018 | Case of the Month

History

A 24 year old lady presented with an 18 month history of a rash on her right forearm. The rash, which was periodic, would arise as an asymptomatic red rash that would gradually darken and fade over a period of 2-3 weeks. This problem had occurred on five occasions. There was no other relevant personal or family history of skin problems. The patient took the occasional NSAID as a painkiller, but was otherwise well.


Examination

On examination there was a smooth red patch on the flexural surface of the right forearm. Photographs on the patient's phone showed the rash in its hyperpigmented state. 


Investigations

What is the diagnosis?


Images

Diagnosis

RevealHide the answer

 The diagnosis is a fixed drug eruption (FDE) to the NSAID.
 

  • Chronology of a FDE- symptoms occur within 48 hours of commencing the medication
     
  • Clinical features:
    • Distribution - the lips, face, distal limbs, hands & feet, glans penis and perianal skin are the most common site. The rash occurs at same site on re-exposure
    • Morphology - well-demarcated erythematous plaque that may blister
    • Tends to heal with post-inflammatory hyperpigmentation
       
  • Large numbers of drugs implicated. The most commonly associated drugs are tetracyclines, sulphonamides, NSAID and quinine
     
  • Occasionally the eruption is secondary to a chemical in food, agents have included sodium benzoate (a preservative in acidic foods eg carbonated drinks, fruit juice and jam), Splenda ® (an artificial sweetener), green tea and tartrazine (an orange colouring in food and drinks - now seldom used). Cannabis can also cause a fixed drug eruption 

For more information please refer to the relevant chapter on adverse cutaneous drug eruptions

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