Coagulation Practice Question

A 4 year old male patient presents with delayed healing of minor skin abrasions and excessive bleeding. Workup reveals a factor XIII deficiency. Which of the following is true regarding this patient's condition?

Show Answer and Explanations

The patient's fibrin clots are unstable. — Correct answer

Correct. Factor XIII is a heterotetramer which has two catalytic A subunits (chromosome 6, made by monocytes, macrophages and platelets) and two carrier B subunits (chromosome 1, made by the liver). Thrombin activates factor XIII, which then cross links fibrin. This mechanism forms the basis of the screening test for factor XIII deficiency, called the clot solubility test. For the test, the patient's plasma is incubated with thrombin and calcium to promote fibrin clot formation. Since the fibrin is not crosslinked, it can be dissolved by the addition of urea or acid. Confirmation is with a factor XIII activity assay.

The patient's PTT, PT and thrombin time are prolonged.

Incorrect. Factor XIII deficiency shows an abnormal clot solubility test, since the fibrin clot is not stable without factor XIII crosslinking the fibrin strands. The PT, PTT and thrombin times are normal.

The patient has an X-linked recessive condition.

Incorrect. The condition is autosomal recessive. Factor XIII consists of two A subunits and two B subunits. Most mutations are in the catalytic A subunit.

The patient's prognosis is very poor.

Incorrect. The prognosis is good, and most patients do not develop inhibitors to treatment with factor XIII replacement. FFP and cryoprecipitate are alternative treatment options.

The patient should receive treatment with DDAVP.

Incorrect. DDAVP can be used to treat mild hemophilia A (factor VIII deficiency), von Willebrand disease (not effective for type 2B), or uremic induced platelet dysfunction.

Summary