Acquired C1 inhibitor deficiency associated with systemic lupus erythematosus, secondary antiphospholipid syndrome and IgM monoclonal paraproteinaemia.

In this case report, a woman is described who developed systemic lupus erythematosus at the age of 36 years affecting the central nervous system and kidneys, showing the serological evidence of an acquired C1 inhibitor deficiency, but also developing an antiphospholipid syndrome and IgM lambda type paraproteinemia. During the 25 years follow-up she did not show any signs of angioedema. Although the immunological abnormalities are still constantly present, the disease has been quiescent since the past three years. The possible pathophysiology of clinical and laboratory features are discussed.