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Acquired dysfibrinogenemia caused by monoclonal production of immunoglobulin light chain

Molecular Pathology Laboratory, Christchurch School of Medicine and Health Sciences, Christchurch, New Zealand; Department of Biochemistry, Canterbury Health Laboratories, Christchurch, New Zealand; Blood Transfusion Service, Dunedin Hospital, Dunedin, New Zealand

Correspondence: Dr. Amy Dear, Department of Chemistry and Biochemistry, University of Colorado at Boulder, 215 UCB, Boulder, CO 80309, USA; Tel: +1.720.635.0623; amy.dear{at}colorado.edu

Disorders of fibrinogen are usually caused by genetic mutations that result in low protein levels (hypofibrinogenemia) or an abnormal molecule (dysfibrinogenemia). However, environmental and plasma factors can have an acquired effect on its expression or function. For example, antibodies can bind fibrinogen and/or fibrin to interfere with polymerization and inhibit coagulation. The objective here was to determine the cause of dysfibrinogenemia in a 63-year-old man. Despite a low functional fibrinogen concentration and prolonged thrombin time, no inherited fibrinogen abnormality could be detected after extensive protein analysis and gene sequencing. Thus, electrophoresis methods and fibrinogen binding studies were used to establish the cause of the acquired dysfibrinogenemia. An immunoglobulin light chain was found to bind fibrinogen as a monomer. It had no significant effect on fibrinopeptide release, but caused substantial defects in all other stages of thrombin-catalyzed fibrin polymerization. Binding to fibrinogen also seemed to prevent the light chain from being filtered through the kidneys, causing only low levels of it in the urine. Once in the urine, the chain lost its anti-fibrinogen activity, apparently due to dimerization. The 63-year-old patient acquired dysfibrinogenemia from a monoclonal production of light chain that bound and inhibited the function of fibrinogen. At age 64.5 he was diagnosed with monoclonal gammopathy of undetermined significance, explaining the abnormal immunoglobulin chain production. This case was particularly unusual in that the inhibition of fibrin polymerization was caused by a single immunoglobulin light chain, rather than by a whole antibody molecule.

Key words: fibrinogen, acquired dysfibrinogenemia, immunoglobulin light chain, monoclonal gammopathy of undetermined significance (MGUS).