Severe Systemic Lupus Erythematosus presentation in patient with alternative complement pathway mutations

Systemic lupus erythematosus (SLE) is an autoimmune disease with broad clinical manifestations characterized by the production of autoantibodies1 which can have multi -organ involvement2 with tissue damage produced mainly by complement activation by immune complexes (IC).3 As a result of this activation, patients present hypocomplementaemia during disease flares, but C3 and C4 levels are expected to return to normal range between flares. Complement alternative pathway activation with C3 deficiency has been reported in SLE manifestations, notably lupus nephritis.4,5 However, this association is unclear, as partial deficiencies of complement proteins have not been associated with SLE.6,7 Inherited deficiencies of several complement proteins strongly predispose to SLE while mutations of complement inhibitors are found mostly in kidney diseases such as atypical haemolytic uraemic syndrome (aHUS).