Microangiopathic haemolytic anaemia secondary to lupus nephritis: an important differential diagnosis of thrombotic thrombocytopenic purpura.

Systemic lupus erythematosus (SLE) has been described as a cause of microangiopathic haemolytic anaemia (MAHA), however there is little literature to support this assertion. We report on three patients presenting with SLE and MAHA with a clinical picture indistinguishable from thrombotic thrombocytopenic purpura (TTP), who had underlying lupus nephritis. They all had significant proteinuria and normal Von Willebrand Factor cleaving protease (vWF-CP) levels. Their MAHA fitted better for haemolytic syndrome (HUS) and their cerebral signs were explained either by malignant hypertension or cerebral lupus. Their MAHA only improved when the appropriate treatment for lupus nephritis was given. We propose that the previously described association between SLE and MAHA, in actuality relates to the underlying presence of lupus nephritis causing haemolytic uraemic syndrome, not TTP. Significant proteinuria was present in all cases of MAHA due to lupus nephritis, so may be a useful discriminatory sign. Furthermore the demonstration of a normal vWF-CP assay aided in the distinction between TTP and MAHA due to lupus nephritis. All our patients responded to mycophenolate mofetil suggesting this may be useful in other cases of lupus nephritis causing HUS.