Molecular bases of CRM+ factor X deficiency: a frequent mutation (Ser334Pro) in the catalytic domain and a substitution (Glu102Lys) in the second EGF-like domain

Genotypes and phenotypes characterization of 17 Iranian patients with inherited factor X deficiency: identification of a novel mutation: Leu487Phe

Factor X deficiency is a rare bleeding disorder that affects almost 1 : 1000 000 people worldwide. It derives from multiple mutational changes in the factor X gene (F10). The main objective of the present study was to determine a consistent correlation between the clinical presentations and causative genotype. The phenotype and genotype of 17 Iranian patients with reduced factor X activity (FX:C) from 14 unrelated families were analyzed to screen factor X gene expression for any possible mutations and function alteration. Analysis of the sequencing results led to the identification of eight different mutations besides a single nucleotide variation. One of the mutations was novel (Leu487Phe) as studied by means of online analysis programs and molecular modeling. Eight patients were homozygote; three were heterozygote, while six out of 17 patients were symptomatic cases without any mutations. The Arg40Thr missense mutation was detected in three patients including two siblings and was associated with severe bleeding symptoms. Also, two patients were identified with Gly262Asp missense mutation which commonly presented with bleeding disorder. Each of the other patients was associated with a unique missense mutation including one novel mutation in which the tentative relation of the mutation to bleeding symptoms is reported. Mutations leading to a FX:C of less than 1% are associated with severe bleeding symptoms confirming the strong correlation between clinical severity and FX:C. The novel Leu487Phe mutation with FX:C of 13% may have possible negative effects on factor X protein function resulting in minor clinical manifestation.

Factor X deficiency: clinical manifestation of 102 subjects from Europe and Latin America with mutations in the factor 10 gene

Inherited factor X deficiency (FXD) is a rare (1:1,000,000) recessive bleeding disorder. The clinical and laboratory phenotypes of FXD are poorly correlated and few regional studies on the genotype and the clinical manifestations of FXD are known. To understand the association between clinical manifestations and causative genotype, detailed evaluation of bleeding pattern in a high number of patients is needed. This international study analysed the phenotype and genotype of 102 subjects from Central Europe (Germany, Poland and Slovakia) and Latin America (Costa Rica and Venezuela) with causative mutations in the F10 gene, via sequencing. Twenty-eight homozygous, seven compound-heterozygous and 67 heterozygous FXD subjects were characterized. Twenty-nine different causative mutations, including 15 novel mutations, were analysed. Spontaneous bleeding symptoms in 42 symptomatic individuals (26 homozygous, seven compound heterozygous and nine heterozygous) comprised easy bruising (55%), haematoma (43%), epistaxis (36%), haemarthrosis (33%), intracranial haemorrhage (ICH; 21%), and gastrointestinal (GI) haemorrhage (12%). The manifestation of bleeding symptoms in 9 of 67 (13%) symptomatic heterozygous subjects is described. The bleeding patterns of the enrolled patients showed differences that are associated with the types of F10 mutation, and the corresponding genotypes. The homozygous patients were evaluated for genotype-phenotype correlation. The results suggested that ICH seems to be associated with the F10 mutation Gly380Arg, and possibly with the mutations IVS7-1G>A and Tyr163delAT. A tentative association of other mutations to severe symptoms such as haemarthrosis and GI haemorrhage is reported. The severity of FXD, the genotype-phenotype association, and the results of regional studies are discussed.