A novel mutation in ALK-1 causes hereditary hemorrhagic telangiectasia type 2

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant bleeding disorder and has two variants, HHT1 and HHT2, associated with mutations in the ENG and ALK-1 genes, respectively. We identified one Chinese HHT2 family to investigate the pathogenic gene and its possible mechanism of action by mutation screening and functional study. One substitution mutation (1717C>T) in exon 10 of the ALK-1 was found by sequencing of all exons of ENG and ALK-1 and caused a R479X mutation in the ALK-1 protein. ALK-1 mRNA and plasma thrombomodulin were measured by real-time quantitative PCR and ELISA, respectively. There was no significant difference in the expression levels of ALK-1 mRNA between patients and healthy individuals. A significantly higher level of thrombomodulin was found in HHT patients. These findings indicate that the mutation causes truncation of the ALK-1 protein at the post-transcriptional level; the plasma thrombomodulin may provide an easy diagnostic indicator in HHT patients.

Symptoms of inherited factor V deficiency in 35 Iranian patients

The type of bleeding symptom has been evaluated in 35 Iranian patients with an inherited deficiency of factor V, with plasma levels between 1% and 10%. The most frequent symptoms included epistaxis and excessive bleeding after surgery. Haemarthroses and muscle haematomas were less common, even in severely deficient patients. More severe symptoms such as gastrointestinal and central nervous system bleeding were rare. The severity of bleeding symptoms was only partially related to the degree of factor V deficiency in plasma. On the whole, human factor V deficiency is characterized by a moderately severe bleeding phenotype.