FACTOR VIII AND IX (8 & 9)

In the realm of rare genetic phenomena, a truly extraordinary case unfolds: an individual presenting both severe haemophilia B and mild haemophilia A, each attributable to distinct genetic mutations. The patient’s journey is marked by a lifelong awareness of FIX deficiency, only to reveal the unexpected occurrence of mild haemophilia A at the age of 42, following a routine dental procedure. Genetic scrutiny unveiled a point mutation in exon 2 of the F9 gene (c.223C>T, p.R75X) as the cause of haemophilia B, while a separate mutation in exon 4 of the F8 gene (c.545A>C, p.D182A) was identified as the culprit behind haemophilia A. The maternal lineage played a crucial role, with the mother carrying the F8 mutation but not the F9 mutation, suggesting a de novo F9 mutation. Remarkably, an inadvertent connection emerged as a German family exhibited mild haemophilia A with the same F8 mutation, highlighting a shared ancestral link confirmed through F8 haplotype analysis. This extraordinary revelation not only validates the extreme rarity of simultaneous haemophilia A and B but also unravels a captivating genetic tapestry with common roots between the German and Lithuanian families, offering profound insights into the genetic landscape.