From the Guidelines
Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are distinct thrombotic microangiopathies with different pathophysiologies, clinical presentations, and management strategies, and it is crucial to differentiate between them to provide appropriate treatment and improve patient outcomes. The key differences between TTP and HUS lie in their underlying causes, clinical manifestations, and laboratory findings. TTP is characterized by ADAMTS13 deficiency, typically affects adults, and presents with the pentad of fever, thrombocytopenia, microangiopathic hemolytic anemia, neurological symptoms, and renal dysfunction, as noted in studies on thrombotic microangiopathies 1. Some key features of TTP and HUS are:
- TTP:
- ADAMTS13 deficiency (activity <10%)
- Typically affects adults
- Presents with fever, thrombocytopenia, microangiopathic hemolytic anemia, neurological symptoms, and renal dysfunction
- Laboratory findings include severe thrombocytopenia (<30,000/μL), schistocytes on peripheral smear, elevated LDH, and normal coagulation studies
- HUS:
- Typically caused by Shiga toxin-producing E. coli (STEC) or complement dysregulation
- Predominantly affects children
- Presents with the triad of thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury, often following bloody diarrhea
- Patients typically have less severe thrombocytopenia (>30,000/μL) and more prominent renal failure The management of TTP and HUS also differs significantly, with TTP requiring immediate plasma exchange and corticosteroids, often with rituximab, while HUS is managed supportively for STEC-HUS, and with complement inhibition using eculizumab for atypical HUS, as discussed in recent guidelines on thrombotic microangiopathies 1. The distinction between TTP and HUS is critical, as plasma exchange is lifesaving in TTP but not effective in HUS, while complement inhibition is essential for atypical HUS but unnecessary in TTP.
From the Research
TTP vs HUS Comparison
- TTP (Thrombotic Thrombocytopenic Purpura) and HUS (Hemolytic Uremic Syndrome) are two related conditions with similar clinical features, but separate pathogenesis 2.
- Both conditions have a substantial mortality rate, even with currently available treatments 3.
- Plasma exchange is the recommended treatment for TTP, while supportive therapy, including dialysis, is the most effective treatment for HUS 2.
Treatment Options
- High-dose plasma infusion may be an efficient treatment for TTP/HUS in patients who cannot have early plasma exchange 3.
- Plasma exchange with fresh frozen plasma is the most effective treatment available for TTP 2, 4, 5.
- Corticosteroids may be used as an adjuvant treatment for TTP 6.
- Vincristine may be used as a salvage therapy for refractory TTP patients 6.
Outcomes
- Complete remission rates for TTP patients treated with plasma exchange range from 60-100% 3, 5, 6.
- Mortality rates for TTP patients range from 10-40% 3, 5, 6.
- Relapse rates for TTP patients range from 10-30% 3, 5, 6.
- HUS patients have a better prognosis with supportive therapy, including dialysis, with a lower mortality rate compared to TTP patients 2.