A 52-year-old man from Bangalore presents with sudden-onset severe headache, confusion, and visual disturbance. His BP is 168/105 mmHg. CBC shows Hb 9.8 g/dL, WBC 8.2 × 10⁹/L, and platelets 45 × 10⁹/L. Peripheral blood smear reveals fragmented RBCs (schistocytes), polychromasia, and reduced platelet numbers. Serum creatinine is 2.1 mg/dL, and LDH is markedly elevated at 1850 U/L. What is the most appropriate immediate next step?

Explanation

## Diagnosis: Thrombotic Microangiopathy (TMA) — Likely Thrombotic Thrombocytopenic Purpura (TTP) ### Peripheral Blood Smear Interpretation **Key Point:** Schistocytes (fragmented RBCs, helmet cells, triangle cells) on peripheral smear indicate **mechanical hemolysis** from fibrin strands in the microvasculature—the hallmark of thrombotic microangiopathy. **High-Yield:** The classic pentad of TTP: 1. Microangiopathic hemolytic anemia (schistocytes, elevated LDH, low haptoglobin) 2. Thrombocytopenia (platelet consumption) 3. Neurologic symptoms (confusion, headache, focal deficits) 4. Renal dysfunction (elevated creatinine) 5. Fever (present in ~50% of cases) In this case: **5/5 criteria present** → TTP until proven otherwise. ### Why Plasma Exchange Is the Immediate Next Step **Clinical Pearl:** TTP is a **medical emergency** with mortality >90% if untreated. Plasma exchange must be started **before** confirmatory testing (ADAMTS13) because: 1. **Time-sensitive:** Delay of even hours increases mortality and morbidity (neurologic sequelae, renal failure). 2. **Pathophysiology:** TTP is caused by ADAMTS13 deficiency → uncleaved von Willebrand factor (vWF) multimers → platelet microthrombi. 3. **Plasma exchange mechanism:** - Removes pathologic vWF multimers - Replaces deficient ADAMTS13 - Rapidly reverses platelet consumption **Warning:** Do NOT wait for ADAMTS13 results before starting plasma exchange. The test takes 24–48 hours; the patient may deteriorate irreversibly in that time. ### Management Algorithm ```mermaid flowchart TD A[Schistocytes + thrombocytopenia + neurologic/renal symptoms]:::outcome --> B{Clinical suspicion of TMA?}:::decision B -->|Yes| C[Start plasma exchange IMMEDIATELY]:::urgent C --> D[Send ADAMTS13, LDH, haptoglobin, coagulation panel]:::action D --> E{ADAMTS13 severely deficient?}:::decision E -->|Yes| F[Confirm TTP - continue plasma exchange daily]:::action E -->|No| G[Consider HUS or other TMA - adjust therapy]:::action F --> H[Monitor platelet count, LDH, creatinine daily]:::action ``` **Mnemonic:** **PLASMA FIRST** — Plasma exchange before any other intervention in suspected TTP. ### Differential: TTP vs HUS | Feature | TTP | HUS | |---------|-----|-----| | **ADAMTS13** | Severely deficient (<10%) | Normal | | **Neurologic symptoms** | Common (60–65%) | Rare | | **Renal involvement** | Mild-moderate | Severe (often dialysis-dependent) | | **Prodrome** | Nonspecific illness | Bloody diarrhea (Shiga toxin–producing E. coli) | | **Plasma exchange response** | Excellent | Limited benefit | **Key Point:** In this case, prominent neurologic symptoms + thrombocytopenia + mild renal dysfunction = **TTP phenotype** → plasma exchange is appropriate even before ADAMTS13 confirmation. [cite:Harrison 21e Ch 109; Robbins 10e Ch 13]