Affiliation: Jefferiss Research Trust Laboratories, Wright-Fleming Institute, Imperial College London, St Mary's Campus, Norfolk Place, London W21 PG, UK.
Mycoplasma pneumoniae causes upper and lower respiratory-tract disease. In addition, extra-pulmonary diseases may occur at the same time as the pulmonary infection or soon after. These complications may involve neurological, dermatological, musculoskeletal, cardiovascular, gastrointestinal, renal and hematological systems, or more than one of these. Complications which are dermatological, musculoskeletal and gastrointestinal are seen most frequently (15-50%) but are not as serious as nervous, cardiac and blood disorders. The mechanism behind the development of these complications is largely immunological. The extent to which autoimmune phenomena are responsible varies, evidence for this being greatest for hematological disorders and least for gastrointestinal ones.