A novel Cys328-terminator mutant implicated in severe coagulation factor XIII deficiency: a case report

Molecular basis of rare congenital bleeding disorders

Rare bleeding disorders (RBDs), including factor (F) I, FII, FV, FVII, combined FV and FVIII (CF5F8), FXI, FXIII and vitamin-K dependent coagulation factors (VKCF) deficiencies, are a heterogeneous group of hemorrhagic disorder with a variable bleeding tendency. RBDs are due to mutation in underlying coagulation factors genes, except for CF5F8 and VKCF deficiencies. FVII deficiency is the most common RBD with >330 variants in the F7 gene, while only 63 variants have been identified in the F2 gene. Most detected variants in the affected genes are missense (>50% of all RBDs), while large deletions are the rarest, having been reported in FVII, FX, FXI and FXIII deficiencies. Most were located in the catalytic and activated domains of FXI, FX, FXIII and prothrombin deficiencies. Understanding the proper molecular basis of RBDs not only can help achieve a timely and cost-effective diagnosis, but also can help to phenotype properties of the disorders.

Genetic landscape in coagulation factor XIII associated defects – Advances in coagulation and beyond

Coagulation factor XIII (FXIII) acts as a fine fulcrum in blood plasma that maintains the balance between bleeding and thrombosis by covalently crosslinking the pre-formed fibrin clot into an insoluble one that is resistant to premature fibrinolysis. In plasma, FXIII circulates as a pro-transglutaminase complex composed of the dimeric catalytic FXIII-A encoded by the F13A1 gene and dimeric carrier/regulatory FXIII-B subunits encoded by the F13B gene. Growing evidence accumulated over decades of exhaustive research shows that not only does FXIII play major roles in both pathological extremes of hemostasis i.e. bleeding and thrombosis, but that it is, in fact, a pleiotropic protein with physiological roles beyond coagulation. However, the current FXIII genetic-epidemiological literature is overwhelmingly derived from the bleeding pathology associated with its deficiency. In this article we review the current clinical, functional, and molecular understanding of this fascinating multifaceted protein, especially putting into the same perspective its genetic landscape.

Prenatal diagnosis of factor 13 deficiency and its recurrence

A young third gravida was referred with prenatal diagnosis of factor XIII deficiency at 20 weeks of pregnancy for Medical Termination of Pregnancy (MTP). Her first baby, who was born by emergency Lower Segment Caesarean Section (LSCS) for fetal distress, had intracranial haemorrhage in the early neonatal period and was investigated elsewhere and diagnosed to have factor XIII deficiency. The child currently has global developmental delay and cerebral palsy. The mother had a second-degree consanguineous marriage and the couple were diagnosed to be carriers of factor XIII deficiency. She had lot of barriers to get prenatal diagnosis during the second pregnancy and it ended up in Intra Uterine Fetal Death (IUFD) at 27 weeks. During the current pregnancy, prenatal diagnosis (PND) was done only after the second trimester amniocentesis and the genetic mutation was F13 A1, Ex12, C.1687 G>A. Second trimester MTP in a previous scarred uterus was difficult as it is essential to avoid scar rupture. PND during the first trimester is ideal.