LabMed

High Molecular Weight Kininogen Deficiency – Congenital

At a Glance

A patient with high molecular weight kininogen (HK) deficiency presents with a long activated partial thromboplastin time (APTT; >60 sec), normal prothrombin time (PT), and no history of bleeding. High molecular weight kininogen deficiency is quite rare; it is the least common of all the blood coagulation proteins deficiencies. In North America, it has only been seen in individuals with an African-American background. This disorder is autosomal recessive in inheritance. Its deficiency is not associated with bleeding.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

The APTT and a specific high molecular weight kininogen procoagulant assay should be ordered. One has to exclude an inhibitor to HK by performing a specific inhibitor assay.(Table 1)

Table 1

Test Results Indicative of the Disorder
APTT HK Assay Lupus Anticoagulant
>60 sec <10% No evidence

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

Anticoagulants like unfractionated heparin, dabigatran, hirudin, bivalirudin, argatroban, warfarin, enoxaparin, or fondaparinux could interfere with results.

What Lab Results Are Absolutely Confirmatory?

The tests result that is confirmatory is a low HK assay with no evidence of an inhibitor to HK.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

HK assay with normal assays for factor XII, XI, IX, and VIII and prekallikrein confirm the clinical diagnosis.

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

Anticoagulants interfere with all coagulant-based assays. One has to be certain that the samples do not have anticoagulants in them. Also, high plasma lipid and serum bilirubin will interfere with certain coagulant readers.

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