Abstract
This article addresses the issue of thromboembolic disorders associated with the prothrombin
G 20210A gene mutation, with heparin cofactor II (HC-II) defects and with primary
(essential) thrombocythemia. The prothrombin gene mutation is of recent discovery,
is inherited as an autosomal dominant disorder, and seems to be highly prevalent in
the general white population. The incidence is almost as high as that known for factor
V Leiden. Both venous and arterial thromboses are noted, especially deep venous thrombosis,
including cerebral venous events and myocardial infarction. As with other congenital
thrombophilic states, additional risk factors or multiple defects seem to precipitate
the events. Although initially elevated plasma prothrombin levels were described in
these patients, this is no longer valid for all patients. At this time there is no
easy screening test to detect this defect, but, because of the high prevalence, prothrombin
G 20210A gene mutation should routinely be assayed for in thrombophilic patients.
The assoication between HC-II defects and thromboembolism is more controversial, and
reports both confirming and denying this assoication have been described. The congenital
form of HC-II defect is autosomal dominant. HC-II can be determined by its activity
and immunologically. HC-II defects very likely play a role in conjunction with other
congenital or acquired defects. Acquired HC-II defects are found in association with
systemic disseminated intravascular coagulation (DIC) but not with local activation
of the hemostasis system. HC-II levels are also decreased in preeclamptic women, and
newborns have physiologically low levels. HC-II defects in thrombophilic patients
should be considered after the more common disorders have been ruled out. Primary
(essential) thrombocythemia can be associated with both thromboembolic events and
bleeding. Typical thrombotic manifestations are erythromelalgia and microvascular
thrombosis. Also, pregnant females suffer high rates of complications, such as spontaneous
abortion. A number of treatment modalities are at present available to not only decrease
platelet counts but also manage thromboembolic events.
Keywords:
Thrombosis - embolism - prothrombin G20210A gene mutation - heparin cofactor II -
primary thrombocythemia - essential thrombocythemia
