Thrombotic microangiopathy with renal involvement: Case report and considerations on differential diagnosis and treatment

The first approach to a patient with thrombotic microangiopathy (TMA) involves differentiating thrombotic thrombocytopenic purpura (TTP) from hemolytic uremic syndrome (HUS), since both pathogenesis and treatment differ. Case-by-case decision making based on all the clinical, laboratory and response-to-therapy criteria can result in an accurate diagnosis, leading to the most appropriate therapy and a better chance of improving clinical outcome while preserving organ function. We report the case of a 21-year-old female admitted for TMA characterized by severe renal involvement and no neurological symptoms. Clinical onset occurred after a three-day long episode of diarrhea. First analysis showed no evidence of shiga toxin-producing E. Coli (STEC) and revealed severely deficient ADAMTS13 activity, which is common in TTP. After an initial response to steroids and plasma exchange therapy (PEX), the patient became PEX-dependent. A complete remission and PEX-independence was achieved by a B cell depletion therapy with Rituximab. Results of the subsequent genetic analysis showed a new heterozygous variant p.Arg448Leu, as an isolated mutation, in the complement factor I gene.