Factor VII (Labile Factor or Proconvertin) Deficiency (Alexander’s Disease)
Factor VII (FVII), or proconvertin, deficiency was first recognized in 1951. Considered the most common of rare bleeding disorders its incidence is estimated at 1 per 300,000-500,000. It is inherited in an autosomal recessive fashion, meaning both parents must carry the gene to pass it on to their children; it affects men and women equally.
FVII is a protein that, when bound to tissue factor, initiates the clotting cascade, which leads to the formation of a blood clot.
Symptoms
Symptoms are usually linked to the level of FVII in the blood, but not always. For instance, some people with low FVII levels may have mild symptoms.
Babies are often diagnosed with FVII deficiency within the first 6 months of life, after sustaining a bleed in the central nervous system, such as an intracranial hemorrhage, or gastrointestinal tract. People with severe FVII deficiency experience joint and muscle bleeds, easy bruising and bleeds after surgery. Bleeds can also occur in the skin, mouth, nose and genitourinary tract. Women often experience severe menorrhagia, long, heavy periods.
Testing
Diagnosis is made through activated partial thromboplastin time (aPTT) test and prothrombin time (PT) test. Diagnosis can be confirmed with a FVII assay. Acquired factor VII deficiency can occur in patients with liver disease and vitamin K deficiency, and in those taking oral anticoagulants.
Treatment
The main treatment for FVII deficiency is recombinant factor VIIa (rFVIIa). Prothrombin complex concentrates (PCCs) can also be used, but the amount of factor VII they contain can vary considerably. Fresh frozen plasma (FFP) is another option. In some patients, the use of FFP has led to blood clots.