A case history recently published in the BMJ highlights one of those uncommon but very diagnoseable conditions if you just spot the clues.According to the French authors, the 62 year old man presented with a history of recurrent oral ulcers sometimes accompanied by laryngitis and conjunctivitis.During one of these episodes he had developed an acute fever, a sore throat when swallowing and laryngitis – he had sought medical attention and was prescribed ibuprofen and clarithromycin. Two days after this, the man developed conjunctivitis, erosions in the mucosal membrane in the mouth and skin lesions.Not unsurprisingly, the man’s attending doctors though he had Stevens-Johnson syndrome and sent him to hospital. Full examination showed painful diffuse erosions of mucous membranes not only of the oral cavity but also of the nose, the epiglottis and the glans. The skin lesions were noted to be target lesions involving three raised concentric red rings and they were found on the trunk, lower limbs and scrotum. He was febrile, fatigued and eating was painful.Diagnostic tests showed a raised CRP but little else. The skin biopsy showed a dense lichenoid lymphocytic infiltrate.So did he have Stevens-Johnson syndrome?Apparently not. The target lesions with their three concentric rings and the widespread oral, ocular and genital mucous membrane erosions are in fact suggestive of erythema multiforme, and specifically because of the fact more than one mucous membrane was involved, the more severe type of erythema multiforme – erythema multiforme major.The authors did concede that erythema multiforme is frequently confused with Stevens-Johnson syndrome, and even toxic epidermal necrolysis (TEN), which are life-threatening conditions.The features that helped distinguish this as a case of erythema multiforme rather than the other more serious alternatives were:

• • the previous episodes of oral ulcers, sometimes with laryngitis and conjunctivitis. Even though erythema multiforme is rare, of the people who do get it some 40% experience multiple recurrences often triggered by the herpes simplex virus.
  • erythema multiforme is generally a post-infectious disease most commonly herpes simplex (which was tricky in this case as viral cultures from the patient’s mouth were negative) whereas 85% of Stevens-Johnson syndrome and toxic epidermal necrolysis cases are drug-induced.
  • erythema multiforme usually begins with systemic symptoms such as fever and then mucosal involvement. The skin lesions typically appear later. In Stevens-Johnson syndrome and toxic epidermal necrolysis the severe cutaneous reaction is usually the first sign of the condition occurring four to 28 days after taking the offending drug.
  • finally the skin lesions are different. As in this case, the typical skin lesions of erythema multiforme are three raised concentric rings that usually respond to topical steroids and oral antihistamines. In Stevens-Johnson syndrome and toxic epidermal necrolysis the lesions are ‘atypical targets with two concentric rings and purpuric macules that evolve into blisters and skin that detaches with finger friction (Nikolsky sign).’

And what happened to this patient?According to the case report, he wound up staying eight days in hospital treated with enteral nutrition, topical steroids and steroid mouthwashes. All the skin and mucosal membrane lesions healed and he fully recovered. Interestingly, he did have minor relapses annually for a number of years but these weren’t severe enough to warrant any further treatment.Ref:BMJ 2017; 359 doi: https://doi.org/10.1136/bmj.j3817