A newborn presents on day 2 of life with extensive skin necrosis over the buttocks and limbs. Biopsy shows microvascular thrombi. Protein C activity is severely deficient. This presentation results from failure of degradation of which pair of factors?

• A Factors IXa and Xa
• B Factors VIIIa and Va ✓
• C Factors XIIa and XIa
• D Fibrin monomers and fibrinopeptide A

Explanation

Activated protein C, with protein S as cofactor, proteolytically inactivates factors Va and VIIIa, the two cofactors of the coagulation cascade. Severe congenital protein C deficiency permits uncontrolled thrombin generation after birth, causing neonatal purpura fulminans with dermal microvascular thrombosis. Factors IXa and Xa are inhibited by antithrombin, not by protein C.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.