A patient with a laceration repaired in the ED returns 15 hours later with excessive bleeding; PT, aPTT, fibrinogen, and platelets are normal. The most likely diagnosis is:

A patient with a laceration repaired in the ED returns 15 hours later with excessive bleeding; PT, aPTT, fibrinogen, and platelets are normal. The most likely diagnosis is:

• A. Chronic DIC
• B. Lupus
• C. Factor XII deficiency
• D. Factor XIII deficiency

Answer: (D)

The key idea is that the problem is in stabilizing the clot, not in clot formation. When PT, aPTT, fibrinogen, and platelets are all normal, yet bleeding persists or recurs after an injury, it points to a defect in the final stabilization step of coagulation. Factor XIII is the enzyme that cross-links fibrin strands to form a stable, insoluble clot. If Factor XIII is deficient, the initial clot can form but remains unstable and is prone to breakdown, especially under physical stress or over time. This produces delayed or recurrent bleeding after a seemingly successful hemostatic plug, which fits a patient who bleeds hours after an ED repair despite normal standard coagulation tests. Standard tests like PT and aPTT are normal because the primary coagulation cascade and platelet function are intact; only the cross-linking of fibrin is impaired. FXIII activity testing (or a clot solubility test) is required to confirm. Other options don’t fit because chronic DIC would show consumption of clotting factors and platelets with abnormal PT/aPTT and low fibrinogen; lupus-related problems can prolong aPTT but don’t specifically cause delayed wound instability; Factor XII deficiency prolongs aPTT but typically does not cause bleeding; Factor XIII deficiency uniquely causes normal routine tests with defective clot stabilization leading to delayed bleeding.

The key idea is that the problem is in stabilizing the clot, not in clot formation. When PT, aPTT, fibrinogen, and platelets are all normal, yet bleeding persists or recurs after an injury, it points to a defect in the final stabilization step of coagulation.

Factor XIII is the enzyme that cross-links fibrin strands to form a stable, insoluble clot. If Factor XIII is deficient, the initial clot can form but remains unstable and is prone to breakdown, especially under physical stress or over time. This produces delayed or recurrent bleeding after a seemingly successful hemostatic plug, which fits a patient who bleeds hours after an ED repair despite normal standard coagulation tests. Standard tests like PT and aPTT are normal because the primary coagulation cascade and platelet function are intact; only the cross-linking of fibrin is impaired. FXIII activity testing (or a clot solubility test) is required to confirm.

Other options don’t fit because chronic DIC would show consumption of clotting factors and platelets with abnormal PT/aPTT and low fibrinogen; lupus-related problems can prolong aPTT but don’t specifically cause delayed wound instability; Factor XII deficiency prolongs aPTT but typically does not cause bleeding; Factor XIII deficiency uniquely causes normal routine tests with defective clot stabilization leading to delayed bleeding.