Serum mycoplasma IgM and IgG were positive, indicating an acute infection. Herpes simplex and varicella zoster virus PCR were negative. Other investigations including blood culture were non-contributory. Chest X-ray showed a peribronchial pneumonia pattern. Based on these findings and the clinical presentation, the diagnosis erythema multiforme (EM) major was made, most likely the result of infection with Mycoplasma pneumoniae.
The patient was admitted to the department of paediatrics and treated with azithromycin 10 mg/kg/day for three days for mycoplasma infection. Further treatment consisted of adequate analgesia and administration of fluid to prevent dehydration.
EM is an acute, immune-mediated skin condition. It is characterised by the distinctive ‘target’ lesions: concentric rings with an outer red ring, an inner pale ring and a red centre. Moreover vesicles, bullae and oedematous, erythematous papules can be observed. The target lesions are usually asymptomatic and occur in a symmetrical acral distribution. In up to 70% of the patients the oral mucosa is affected. The ocular and genital mucosa can also be involved. EM is typically seen in adults between the ages of 20 and 40. The incidence is estimated to be less than 1% per year.1 EM is usually self-limiting and treatment is focused on symptomatic relief. The underlying cause needs to be treated.
However, EM can be caused by numerous potential triggering agents and the exact pathogenesis is still unknown. It is considered to be an immunologically mediated hypersensitivity reaction, most commonly induced by infection. EM has also been associated with malignancy, autoimmune diseases and medication such as antibiotics and anticonvulsants. The most common infectious cause of EM is herpes simplex virus. One of the other less frequently reported causes is Mycoplasma pneumoniae. Infection with Mycoplasma pneumoniae can result in respiratory disorders. The clinical features are fever, tachypnoea, coughing and malaise. Besides pulmonary manifestations, cutaneous disorders can occur in op to 25% of the patients.2
The differential diagnosis of EM may include Stevens-Johnson syndrome (SJS). Controversy exists whether EM and SJS are distinct entities or whether they represent a spectrum of the same disease.3 Furthermore the latest research suggests that Mycoplasma pneumoniae-induced rash and mucositis is a syndrome distinct from SJS and EM because of its considered distinct morphology and disease course.4
If target lesions are observed, Mycoplasma pneumoniae should be included in the differential diagnosis as a possible causative agent.
The authors declare no conflict of interest.