FX deficiency, also known as Stuart-Prower Factor deficiency, is a rare recessive bleeding disorder caused by variants in the F10 gene. Said disorder affects between one in 500,000 and one in a million individuals across the globe. Such a deficiency impedes an individual’s ability to clot, resulting in excess bleeding.
CLASSIFICATION AND DISTRIBUTION OF VARIANTS
- FX variants are classified as having a Type I or Type II phenotype. Type I variants are those resulting in decreased levels of FX antigen and FX activity, whereas Type II variants result in decreased FX activity but normal FX antigen.
- Most FX variants stem from point mutations, yet small insertions and deletions have also been detected throughout the F10 gene. All such variants result in the production of non-functional FX protein or truncated FX which undergoes cellular degradation.
- Whilst FX variants are spread across the entirety of the F10 gene, many are clustered in the serine protease (SP) domain, the catalytically active region of FX.
