A 28-year-old primigravida at 34 weeks presents with BP 160/110 mmHg, proteinuria 3+, and thrombocytopenia (platelets 85,000/µL). Serum LDH is 720 U/L, AST 110 U/L, and she complains of right upper quadrant pain. Which of the following best describes the mechanism by which antithrombin III (AT-III) levels are reduced in this condition?

• A Hepatic synthetic failure leading to decreased AT-III production
• B Renal loss of AT-III due to non-selective proteinuria
• C Dilutional effect from expanded plasma volume
• D Excessive AT-III consumption at sites of endothelial injury due to microthrombus formation ✓

Explanation

In HELLP syndrome (the diagnosis here), AT-III consumption occurs at sites of endothelial damage where microthrombi form, depleting the key anticoagulant. Hepatic synthetic function is not primarily impaired enough to cause AT-III deficiency in HELLP, renal proteinuria in pre-eclampsia is typically selective (not losing large proteins like AT-III), and plasma volume in severe pre-eclampsia is actually contracted, not expanded.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.