SHM's Clinical Quick Talks-Thrombotic Microangiopathies

Pdf Summary

Thrombotic Microangiopathies (TMAs) are a group of disorders characterized by microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and end-organ dysfunction, often involving the kidneys and nervous system. Patients present with symptoms such as unexplained anemia, low platelets, neurological abnormalities, renal failure, and sometimes diarrhea, with fever occasionally present. TMAs include primary types—Thrombotic Thrombocytopenic Purpura (TTP), typical Hemolytic Uremic Syndrome (HUS), and atypical HUS (aHUS)—and secondary types caused by drugs, malignancy, autoimmune disorders, pregnancy-related conditions (e.g., HELLP), infections, transplantation, malignant hypertension, and cobalamin C deficiency.<br /><br />Diagnosis relies on laboratory findings: anemia with schistocytes on blood smear, elevated LDH, low haptoglobin, low platelets, and evidence of organ dysfunction. Specific tests include ADAMTS13 activity and inhibitor assays to differentiate TTP (ADAMTS13 activity <10%) from other TMAs, and assays for shiga toxin in HUS. Coagulation profiles help exclude disseminated intravascular coagulation (DIC). The PLASMIC score predicts the likelihood of TTP and guides urgency for plasma exchange.<br /><br />Treatment is urgently directed at TTP due to its high mortality without therapeutic plasma exchange (TPE). Steroids are used adjunctively, with dosing adjusted based on risk. Rituximab and caplacizumab may be added upon confirmed diagnosis. Typical HUS mainly requires supportive care, including hydration and renal support. Atypical HUS often necessitates anti-complement therapy (eculizumab) alongside plasma exchange if diagnosis is unclear initially. Secondary causes demand targeted management such as discontinuing offending drugs.<br /><br />A clinical case illustrates management: a patient with severe anemia, thrombocytopenia, and neurological symptoms underwent TPE and steroids while awaiting ADAMTS13 results. When ADAMTS13 was confirmed low with inhibitors, TTP was diagnosed and treatment continued. Variations in presentation such as bloody diarrhea or renal failure shift diagnostic consideration toward HUS.<br /><br />References include authoritative reviews on TMA diagnosis and management. Overall, timely identification and appropriate therapy of TMAs, especially TTP, are critical for patient survival.

Asset Subtitle

Jordan Nickols

Keywords

Thrombotic Microangiopathies

Microangiopathic Hemolytic Anemia

Thrombocytopenia

Thrombotic Thrombocytopenic Purpura

Hemolytic Uremic Syndrome

ADAMTS13 Activity

Plasma Exchange Therapy

Eculizumab

PLASMIC Score

Secondary TMA Causes