A 10-year-old boy presents with a history of delayed umbilical stump bleeding and prolonged bleeding after minor trauma. Laboratory investigations reveal a normal PT, normal aPTT, normal platelet count, and normal bleeding time. A clot solubility test using 5M urea demonstrates rapid dissolution of the clot. Which factor deficiency is the most likely cause?

• A Factor VIII
• B Factor XIII ✓
• C Factor IX
• D Factor VII

Explanation

Factor XIII cross-links fibrin monomers to stabilize the clot. Its deficiency produces normal screening tests (PT, aPTT, platelet count, bleeding time) because these only assess initial fibrin formation, not stabilization. The diagnostic hallmark is a mechanically weak clot that dissolves rapidly in 5M urea. Factor VIII and IX deficiencies prolong the aPTT, while Factor VII deficiency prolongs the PT, making them incompatible with the normal labs in this vignette.

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.