Mycoplasma pneumoniae infection associated with urticarial vasculitis mimicking adult-onset Still's disease.

Mycoplasma pneumoniae is well known to be a frequent cause of atypical pneumonia worldwide. However, it may also present with a wide variety of clinical features, including cutaneous symptoms, which are not widely recognised. Urticarial vasculitis occurring with M. pneumoniae has been described to occur in only one other case report. This amalgamation of non-specific clinical symptoms and signs can lead to a diagnostic dilemma. We describe a case of M. pneumoniae infection presenting with extrapulmonary manifestations and urticarial vasculitis, which was misdiagnosed as adult-onset Still's disease (AOSD). Had immunosuppressive therapy been commenced for AOSD in the presence of undiagnosed infection, this may have resulted in potentially serious consequences. This case highlights the need to remain vigilant about diagnosing M. pneumoniae as its serological diagnosis may take weeks and it has many extrapulmonary manifestations, which can masquerade as other conditions.