Unité hémostase clinique, hospices civils de Lyon, groupement hospitalier Est, Lyon, France
Laboratoire d’hémostase, hospices civils de Lyon, groupement hospitalier Est, Lyon, France
Congenital factor XIII (FXIII) deficiency accounts for 6% of rare bleeding disorders in France. FXIII is a protein with a two-fold role: 1) it increases clot strength at the very end of the coagulation cascade; and 2) contributes towards maintaining pregnancy. Around 80% of severe forms of this disorder are revealed by abnormal bleeding when the umbilical cord becomes detached during the neonatal period, and 30% by spontaneous intracranial haemorrhage (ICH). FXIII deficiency cannot be detected using standard tests - prothrombin time and partial thromboplastin time - since FXIII initially acts following initial clot formation. A FXIII functional activity assay is recommended for diagnosis, and a FXII antigen assay is recommended to classify the FXIII deficiency. FXIII-A antigen assays correlate accurately with functional measures and present a very low detection threshold (less than 4%). Their automation therefore makes it possible to specifically measure FXIII, which is indicated when tell-tale clinical signs are observed. In France, treatment is based on the administration of plasma-derived FXIII concentrates (Fibrogammin®), which have a half-life of between 11 and 14 days. In cases of acute haemorrhage, in particular intracerebral haemorrhage, the initial dose should be between 20 and 40 IU/kg. Due to the high risk of ICH, the recommendation is to initiate prophylaxis replacement therapy as soon as the diagnosis has been made. The recommended dose and dosing interval are at least 20-40 IU/kg once every four weeks.