Factor X deficiency: An uncommon presentation of AL Amyloidosis
Factor X deficiency:
An uncommon presentation of AL amyloidosis
Coagulopathies resultant from clotting factor deficiencies can be roughly split into two categories; heritable and acquired.
A reduction in the synthesis or the destruction of individual clotting factors can be caused by a number of genetically inherited mutations. The most common form of heritable factor deficiency is Haemophilia A, where the production of Factor VIII is compromised by an X-linked recessive mutation.
Factor deficiency can also be acquired by the inhibition of clotting factors or reducing their rate of production in patients without genetic defects. The most common acquired deficiencies are Liver disease, systemic lupus erythematosus and anticoagulation.
Helena Biosciences have an extensive range of analytical reagents and factor deficient plasmas for use in the identification of congenital and acquired factor deficiencies.
Light chain (AL) amyloidosis is a haematological disorder charactorised by the deposition of light chain immunoglobulin into tissue. Mutations in the light chain gene result in a tertiary structure prone to conformational changes resulting in the precipitation of insoluble protein. As a result this disease can be closely linked with clonal B-cell disorders such as multiple myeloma and Wäldenstrom’s macroglobulinaemia.
Acquired factor X deficiency is a known complication of AL amyloidosis with a frequency of about 8.7%. The pathophysiology of this deficiency is thought to be adsorption of factor X onto tissue amyloid fibrils therefore reducing the level of functional factor X in the circulation. The resultant coagulopathy is produced by the reduced ability to convert prothrombin to thrombin as this is mediated by activated factor X. Compounding factors associated with AL amyloidosis such as thrombocytopenia and vascular amyloid infiltration result in disproportionately severe symptoms when compared to heritable factor X deficiency.
The severity of factor X deficiency can be directly correlated to the level of amyloid fibrillation. Reducing the level of free light chain using chemotherapy therefore reducing the rate of fibrillation and removing a large source of amyloid fibrils via splenectomy are both shown to reduce the severity of deficiency.
Factor X deficiency as a presenting feature is relatively uncommon at diagnosis of AL amyloidosis (1%), however it has been documented in the literature that factor X deficiency can be the only presenting feature of an AL amyloidosis patient. As a result AL amyloidosis should be considered as a differential diagnosis in all acquired factor X deficiencies.
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