Congenital fibrinogen disorders: an update

Area of Science:

• Hematology
• Genetics
• Molecular Biology

Background:

• Hereditary fibrinogen abnormalities are categorized into quantitative (Type I: afibrinogenemia/hypofibrinogenemia) and qualitative (Type II: dysfibrinogenemia/hypodysfibrinogenemia) defects.
• Type I defects involve absent or low fibrinogen antigen levels, often due to null mutations in FGA, FGB, or FGG genes, impacting fibrinogen assembly or secretion.
• Type II defects present normal/reduced antigen levels with disproportionately low functional activity, primarily caused by missense mutations.

Purpose of the Study:

• To elucidate the classification, genetic basis, clinical manifestations, diagnostic challenges, and therapeutic considerations of hereditary fibrinogen abnormalities.
• To highlight the importance of molecular defect determination for accurate diagnosis, risk stratification (bleeding vs. thrombosis), and enabling prenatal diagnosis.
• To emphasize the need for individualized replacement therapy due to variable pharmacokinetics.

Main Methods:

• Review and synthesis of existing literature on hereditary fibrinogen disorders.
• Analysis of mutation types (null, missense, nonsense) and their correlation with fibrinogen antigen and functional levels.
• Discussion of clinical phenotypes, diagnostic approaches, and treatment strategies.

Main Results:

• Afibrinogenemia and hypofibrinogenemia (Type I) are linked to bleeding and pregnancy loss, while dysfibrinogenemia (Type II) can cause bleeding, thrombophilia, or be asymptomatic.
• Molecular diagnosis is challenging but crucial for distinguishing bleeding risk from thrombotic risk and guiding personalized treatment.
• Genotype-phenotype correlations are complex, and fibrinogen replacement therapy requires careful individual adjustment due to variable pharmacokinetics.

Conclusions:

• Accurate diagnosis of hereditary fibrinogen disorders relies on understanding both quantitative and qualitative defects and their underlying molecular basis.
• Molecular analysis is essential for confirming diagnoses, predicting clinical outcomes, and tailoring therapeutic interventions, particularly for managing bleeding episodes and thrombotic risks.
• Personalized management strategies, including adjusted fibrinogen replacement therapy, are critical for optimizing patient care due to inter-individual variability in treatment response.