What is the classic clinical pentad of Thrombotic Thrombocytopenic Purpura (TTP)?; Fever + Thrombocytopenia + Microangiopathic Hemolytic Anemia (MAHA) + Neurological deficits (transient) + Renal failure. Mnemonic: FAT RN (Fever, Anemia [microangiopathic], Thrombocytopenia, Renal failure, Neurological symptoms)

What enzyme is deficient in TTP?; ADAMTS13 — "A Disintegrin And Metalloproteinase with ThromboSpondin type 1 motif, member 13." It is a plasma metalloprotease that cleaves large (ultra-large) multimers of von Willebrand factor (vWF) into smaller forms.

What is the function of ADAMTS13 in normal hemostasis?; ADAMTS13 cleaves ultra-large (UL) vWF multimers into smaller, less reactive fragments, preventing spontaneous platelet activation and aggregation.

What happens when ADAMTS13 is deficient?; Ultra-large vWF multimers accumulate in plasma → bind platelet surface glycoproteins → spontaneous platelet activation and aggregation → microthrombi in small blood vessels → thrombocytopenia + organ ischemia.

What are the two main causes of ADAMTS13 deficiency in TTP?; 1. Acquired (most common): Inhibitory autoantibodies against ADAMTS13 (sporadic/immune-mediated TTP, iTTP). 2. Inherited (rare): Inactivating mutations in the ADAMTS13 gene → Upshaw-Schulman syndrome (congenital TTP, cTTP).

What is the pathogenesis of microangiopathic hemolytic anemia (MAHA) in TTP?; Microthrombi in small vessels physically shear passing red blood cells → RBC fragmentation → schistocytes (helmet cells) on peripheral blood smear + elevated LDH + low haptoglobin.

What is the predominant organ involved in TTP vs. HUS?; TTP → CNS (neurological symptoms dominate: headache, confusion, seizures, focal deficits). HUS → Kidney (acute renal failure dominates). Severe renal injury is uncommon in TTP.

What is the key morphological finding in TTP?; Hyaline microthrombi (composed of platelets and vWF, NOT fibrin) in arterioles and capillaries throughout the body — especially the brain, kidneys, heart, and adrenal glands. Fibrin is NOT a major component (unlike DIC).

How does TTP differ from DIC in terms of thrombus composition and coagulation tests?; TTP: Thrombi are platelet/vWF-rich (NOT fibrin-rich); PT and aPTT are typically NORMAL. DIC: Thrombi are fibrin-rich; PT and aPTT are PROLONGED. In TTP, the coagulation cascade is NOT primarily activated.

What is the peripheral blood smear finding in TTP?; Schistocytes (fragmented RBCs / helmet cells) — >3–5 per high-power field is significant. Also: thrombocytopenia, low Hb, elevated reticulocyte count.

What are the key laboratory findings in TTP?; 1. Platelets commonly <20,000/μL. 2. Schistocytes on smear (>3–5 per HPF). 3. Markedly elevated LDH (often >1,000 IU/L). 4. Low haptoglobin. 5. Normal PT and aPTT. 6. Elevated indirect bilirubin. 7. Creatinine typically <2.0 mg/dL (less severe renal involvement vs. HUS). 8. Severe ADAMTS13 activity <10% in iTTP.

What clinical scoring tool is used to estimate the probability of ADAMTS13 deficiency in TTP?; PLASMIC score — uses: Platelet count, Lysis (hemolysis markers), Active cancer, Solid organ/stem cell transplant, MCV, INR, Creatinine. A high score predicts severe ADAMTS13 deficiency and guides plasma exchange initiation.

What are the secondary/drug-associated causes of TTP?; Drugs: Ticlopidine (strongest association), Clopidogrel, Cyclosporine, Tacrolimus, Mitomycin C, Gemcitabine, Cisplatin, Bleomycin, Interferon. Other: Pregnancy, HIV infection, SLE, Hematopoietic stem cell transplantation. (Secondary TTP is NOT strongly associated with ADAMTS13 deficiency.)

What is the mainstay treatment of acquired (immune-mediated) TTP?; Therapeutic Plasma Exchange (TPE / plasmapheresis) using FFP or thawed plasma as replacement fluid — removes autoantibodies against ADAMTS13 AND replenishes functional ADAMTS13. Treats successfully in >80% of patients. MUST be started urgently.

Why are platelet transfusions contraindicated in TTP?; They "fuel the fire" — transfused platelets are incorporated into existing microthrombi, worsening thrombosis and organ ischemia. Only given if platelet count <10,000/μL with severe bleeding or for line placement.

What adjunctive therapies are used in TTP alongside plasma exchange?; 1. Glucocorticoids (steroids) — suppress antibody production. 2. Rituximab (anti-CD20) — depletes B-cells, reduces autoantibody production; also reduces relapse risk. 3. Caplacizumab — anti-vWF nanobody that blocks platelet-vWF interaction; shortens time to response and reduces relapses. 4. Bortezomib (refractory cases). 5. Splenectomy (last resort).

What is Upshaw-Schulman syndrome?; Congenital (familial) TTP caused by homozygous or compound heterozygous ADAMTS13 mutations. Onset is often delayed until adolescence or first pregnancy. Episodes are episodic and relapsing. Treated with prophylactic plasma infusions (FFP) to replace ADAMTS13.

What is the key pathological difference between TTP and HUS at the molecular level?; TTP: ADAMTS13 deficiency → ultra-large vWF multimers → platelet aggregation (platelet-mediated TMA). Typical HUS: Normal ADAMTS13; Shiga-like toxin from E. coli O157:H7 → endothelial injury → TMA. Atypical HUS: Complement regulatory protein mutations (Factor H, Factor I, CD46/MCP) → uncontrolled complement activation → endothelial injury.

What triggers clinical TTP episodes in patients with hereditary (congenital) ADAMTS13 deficiency?; ADAMTS13 deficiency alone is NOT sufficient — additional triggers are required, such as: Superimposed endothelial injury (infection, pregnancy, surgery), Prothrombotic states. This explains why symptoms are episodic rather than continuous.

What is the prognosis of TTP if untreated vs. treated?; Untreated: TTP was UNIFORMLY FATAL. With therapeutic plasma exchange (TPE): >80% of patients are successfully treated. Relapses occur in ~30–40% (reduced by Rituximab). Caplacizumab further shortens recovery and reduces relapse frequency.

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