Search

Introduction: Hereditary factor X (FX) deficiency is a rare autosomal recessive bleeding disorder characterized mainly by mild-to-severe bleeding into the mucous membranes, muscles or joints. Previously, treatment options for hereditary FX deficiency were limited mostly to products that may not specify FX content (i.e. fresh frozen plasma and prothrombin complex concentrates) and that have associated safety concerns. To meet the need for a single-factor replacement therapy specifically for use in FX-deficient patients, a high-purity, high-potency, human plasma-derived FX concentrate (pdFX; Coagadex®; Bio Products Laboratory, Elstree, UK) has been developed and approved for treatment of perioperative bleeding and on-demand treatment in FX-deficient patients. Areas covered: The pharmacology, efficacy, and safety of pdFX are discussed, with a review of preclinical studies and clinical trial data that led to regulatory approval of pdFX in the United States and Europe. Expert opinion: As the first single-factor replacement therapy indicated for hereditary FX deficiency, pdFX is a safe and efficacious treatment option in patients aged ≥12 years with hereditary FX deficiency. Clinical studies of pdFX provide a dosing regimen for use in cases of bleeding episodes, surgery, and prophylaxis. Further studies are ongoing regarding use of pdFX long term and in patients aged ≤12 years.

Factor X (FX) deficiency is a rare hereditary coagulation disorder. This is the first case report on the association of FX deficiency and membranoproliferative glomerulonephritis (MPGN) type I. The patient, a 17-year-old male, presented with edema, hypertension, and microscopic hematuria, followed by a mild upper respiratory tract infection. Laboratory tests revealed: serum creatinine 1.6 mg/dl, serum albumin 2.80 g/dl, C3 16 mg/dl and proteinuria (1,800 mg/day). The renal biopsy showed MPGN type I. The coagulation profile prior to percutaneous renal biopsy revealed prolonged prothrombin time and activated partial thromboplastin time values. The patient was given fresh frozen plasma and vitamin K before the biopsy. Further evaluation showed the functional activity of FX was 7% of the norm. This case emphasizes the need for routine coagulation screening before percutaneous renal biopsy.

The cDNA encoding murine coagulation factor X (fX) was isolated and reconstructed from a lambdaZap cDNA library generated from murine liver mRNA. The cDNA contains 1486 bases starting at the 5'-translation initiation codon. It includes an open reading frame of 1443 nucleotides, followed by an 18 residue 3' nontranslated sequence downstream of the first stop codon. and a 3' poly(A) tail. The translation product is composed of a 40-amino acid signal/propeptide region followed by a 441-residue mature protein. The latter is highly homologous to that of human and rat fX. All protein domains of human and rat fX are strictly conserved in mouse fX. The cDNA coding for mouse fX has been expressed in human embryonic kidney 293 cells and generates fX activity measured in a clotting assay using human fX-deficient plasma.

Twenty four cases with rare coagulation disorders were diagnosed over a 4 year period. These included 8 patients with factor X deficiency, 7 with factor XIII deficiency, 4 each with fibrinogen and factor VII deficiency and 1 with factor V deficiency. All these patients had presented with bleeding manifestations. Two patients with factor X deficiency showed interesting clinical presentations, one patient had recurrent deep vein thrombosis and another patient had a pseudotumor of the thigh.

A functional factor X deficiency is described which caused pronounced reduction in the in vitro activation of the extrinsic system while marginally affecting the in vitro activation of the intrinsic pathway. All studies were normal with the exception of a prolonged PT, an elevated factor X antigen, and low factor X activity. Western blot analysis revealed the presence of two factor X species. The abnormal molecule was of higher molecular weight. Interestingly, there was no bleeding associated with this deficiency. The biochemical basis of this defect is currently under investigation.

A factor X molecular variant was identified in a 13-year-old girl affected by a bleeding tendency. Factor X antigen levels and activation by Russel's viper venom (tested both by clotting and amidolytic assays) were normal. Factor X crossed immunoelectrophoresis was found to be identical to that of the control plasma. Factor X functional activity was low (3% of the normal) if tested by PTT-derived assays, whereas it was found at intermediate levels (about 30-50% of the normal) if measured by prothrombin time-derived assays. The defect in the extrinsic activation was more clearly disclosed using as activating agent thromboplastin from ox brain. The factor X of the patient was completely adsorbed by aluminum hydroxide. The parents of the propositus (first degree cousins) showed factor X functional levels compatible with a condition of heterozygosity for the abnormality. This factor X molecular variant appears different from the other ones so far described and was named 'Factor X Roma'.

The first documented case of inherited factor X deficiency in the dental literature is presented. Its ascertainment as a result of postoperative surgical complications illustrates the clinician's need to be familiar with the hereditary bleeding diatheses, as treatment is dependent on the underlying etiology of the specific disorder. In the present case treatment included administration of the antifibrinolytic agent epsilon-aminocaproic acid (EACA) and fresh frozen plasma. On the basis of our findings, a minimal therapeutic level of circulating factor X is estimated to be 15 percent of the normal level. Genetic heterogeneity within the factor X deficiency phenotype is discussed and, on the basis of laboratory findings, a CRM-positive autosomal recessive structural or regulator gene defect is proposed as the etiologic factor in the current case. Forty-nine cases in the literature are reviewed to delineate the pattern of bleeding in hereditary factor X deficiency.

Thirty cases of amyloidosis with factor-X deficiency, including six of our own, were reviewed. Modest deficiency of factor X was often associated with severe bleeding. In many of the cases, clinical bleeding could not be accounted for by deficiency of factor X alone. Other hemostatic defects were found in these patients and probably contributed to the bleeding. Modes of treatment, including the empiric use of corticosteroids and splenectomy, were discussed in light of current knowledge of pathogenesis of this unusual blood clotting disorder. This involves the interaction of amyloid fibrils and blood clotting factors.

A 75-year-old woman developed a haemorrhagic syndrome due to an acquired deficit in factor X whic resulted in death from gastrointestinal bleeding. This deficit was associated with primary amyloidosis. The relationship between the two conditions, the particular features of the haemostatic picutre and the ineffectiveness of replacement therapy are discussed.