Secondary systemic lupus erythematosus: An analysis of 4 cases of uncontrolled hereditary angioedema

The association of systemic lupus erythematosus and hereditary angioedema (HAE) has formed the basis of numerous case reports and is hypothesised to result from consumption of complement C4 with consequent impaired clearance of apoptotic cells. We describe the development of frank lupus or lupus-like syndrome in four HAE patients with uncontrolled angioedema and low levels of serum C4. Measures that limit hypocomplementaemia in HAE may reduce the incidence of secondary SLE.