- Clinical science
Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy, a condition in which microthrombi, consisting primarily of platelets, form and occlude the microvasculature (i.e. the arterioles and capillaries). The other main thrombotic microangiopathy is hemolytic uremic syndrome (HUS). TTP occurs primarily in adults and is typically due to acquired autoantibodies against a proteolytic enzyme that cleaves von Willebrand factor (vWF). It is a clinical diagnosis based on a pentad of findings: fever, neurological abnormalities, thrombocytopenia, microangiopathic hemolytic anemia, and impaired renal function. If TTP is strongly suspected and initial laboratory tests support the diagnosis, treatment should begin immediately, as the condition may be fatal if left untreated. First-line treatment is plasma exchange therapy.
- Primarily adult patients (median age at diagnosis: ∼ 40 years)
- More common in women and black populations
Epidemiological data refers to the US, unless otherwise specified.
- ADAMTS13 deficiency
- Risk factors
TTP is a thrombotic microangiopathy, a condition in which microthrombi form and occlude the microvasculature; . The other main thrombotic microangiopathy is (HUS). The two conditions have some pathophysiological similarities and share some clinical findings. However, they have distinct etiologies, with TTP being caused by a deficiency of ADAMTS13.
- Autoantibodies or gene mutations → deficiency of ADAMTS13
- vWF accumulation on endothelial cell surfaces
- Platelet adhesion and microthrombosis
- Red blood cells (RBCs) are fragmented by microthrombi blockages, resulting in hemolytic anemia.
- Microthrombi block arterioles, capillaries → end-organ ischemia and damage, especially in the brain and kidneys (potentially resulting in acute kidney injury or stroke).
TTP patients are typically previously healthy adults. The pentad of clinical findings consists of:
- Neurological signs and symptoms
- Low platelet count (i.e. thrombocytopenia)
- Microangiopathic hemolytic anemia
- Impaired renal function
The typical patient is a previously healthy adult presenting with mental status changes, fever, petechiae, fatigue, and pallor. Laboratory tests will then indicate hemolytic anemia and possibly acute kidney injury (AKI). Impaired kidney function may not be present, and only a minority of patients will present with all five clinical findings.
- Peripheral blood smear
- Serum chemistry
ADAMTS13 activity and inhibitor testing
- ↓ ADAMTS13 activity
- Not a routinely available test and should be used for confirmation only
- Identification of secondary causes; (e.g., tests for pregnancy; , SLE, HIV, malignancy)
- See .
The differential diagnoses listed here are not exhaustive.
Treatment should be started after a presumptive diagnosis is made based on clinical features and initial labs (e.g., blood count, peripheral smear, creatinine).
- Monitoring and correction
- Prompt initiation of plasma exchange (PEX) therapy
- Glucocorticoids (e.g., prednisone 1 mg/kg per day orally)
- Rituximab is reserved for severe cases.
- Platelet transfusion should only be reserved for patients who are bleeding or require an invasive procedure.
- Treatment is considered successful after:
TTP requires urgent diagnosis and treatment! Waiting for test results to confirm ADAMTS13 deficiency should not delay treatment.
TTP can result in microthrombus formation and complications in many organs of the body.
- CNS: seizures, coma; , stroke, paresis
- GI tract: hemorrhagic colitis; bowel necrosis, perforation, stricture; peritonitis; intussusception
- Heart: ischemia and fluid overload
- Pancreas: transient or permanent diabetes mellitus
- Liver: hepatomegaly, transaminase elevations
- Kidney: hypertension, chronic kidney disease (CKD), end-stage renal disease (ESRD)
We list the most important complications. The selection is not exhaustive.