A general classification scheme for hereditary FX deficiency divides it into 2 categories: Type 1 and Type 2. Patients with type 1 disease lack the FX and FX functional activity (FX:C) antigens. Type 2 disease patients, on the other hand, have normal antigen levels of FX, while showing an absence of the FX:C antigen.

Hereditary FX deficiency can be further classified based on the levels of FX:C, into mild, moderate and severe groups. Adequate levels of FX:C are considered to be around 10% and patients with levels greater than 20% almost always achieve hemostasis easily [14].

Patients with the mild form of disease show FX:C levels between 5-10 %. They are usually discovered during routine blood tests done for other purposes and may have a family history of the disease. Patients with moderate disease and FX:C levels between 1-5 %, are diagnosed during times of severe hemodynamic stress, namely during surgery, trauma etc. FX:C levels less than 1% are seen in the severe form of the disease. They usually present in the neonatal or early childhood periods.

The hallmark of presentation is abnormal bleeding, varying in severity from mild to severe forms. A typical presentation of patients with FX deficiency includes frequent episodes of bleeding from the mucosal areas, gums, and nose. Recurrent hematomas, hematuria, and hemarthrosis may also be present quite commonly. Women in the childbearing age may have menorrhagia, while pregnant women suffer from an increased risk of miscarriages, antepartum and postpartum hemorrhage. Neonates may show a tendency for intracranial hemorrhage and bleeding from the umbilical stump and the gastrointestinal tract.

Till date, there are no known genetic analyses studies that can be conducted for this disease. However, a high index of suspicion should follow an abnormal clotting profile with prolonged PT (prothrombin time) and APTT (activated partial thromboplastin time). Some hereditary forms of the disease may even have a normal clotting profile.

FX functional activity (FX:C) can be objectively measured using serial dilutions of plasma with low levels of FX. FX levels should be matched with age especially prior to 6 months of age before a patient is labeled as FX-deficient. Neonatal levels reach adult values at about 6 months of age.

Another investigation that is particularly useful is the Russel viper venom (RVV) time. RVV directly activates FX, FV, prothrombin and thrombin and hence, detects FX deficiency easily. FX antigen levels can also be measured using ELISA (enzyme-linked immunosorbent assay) or by certain chromogenic assays. These assays are not used as screening tests because they lack sensitivity in detecting FX-deficient cases.

Treatment is generally not required in patients who are carriers of the disease and those who have FX levels > 10% without any significant history of bleeding [15]. Hereditary FX deficiency is a rare disorder with only a handful of cases reported worldwide. As such, adequate research into its treatment protocols is lacking. However, the United Kingdom Haemophilia Centre Doctors’ Organization have released certain guidelines that may serve as a guide for the management of hereditary FX deficiency and other rare coagulation disorders.

According to this guideline, fresh frozen plasma (FFP) or prothrombin complex concentrates (PCC) can be used to replace the deficient factor X in cases of severe bleeding. Mild-moderate forms of hemorrhage are treated by topical and oral antifibrinolytics. An example is aminocaproic acid, used either as a mouthwash (15 ml every 6 hours) or orally at a dose of 50-100 mg/kg. It provides protective benefit in recurrent mouth or nosebleeds, menorrhagia and other bleeding disorders in women. An alternative is tranexamic acid, which is better tolerated. It is taken orally at a dose of 15mg/kg or 1g every 6 hours.

Antifibrinolytics should be used cautiously if treatment with PCC has already commenced in order to prevent thrombosis. In longstanding cases, it is imperative to monitor FX and FIX levels to guide further management.

The prognosis of hereditary factor X deficiency is good in cases that are diagnosed and treated promptly. However, it may have devastating consequences if it is improperly managed. In general, the prognosis depends on the amount of circulating FX, with extremely low levels increasing the risk of hemorrhage profoundly.

Hereditary FX deficiency persists for life and can result in severe debilitation in the quality of life due to the increased tendency for bleeding, seen especially in states of hemodynamic stress. In infants, bleeds in the central nervous system and from umbilical stumps have resulted in death in some cases. Massive hemorrhages post-surgery are also reported in the absence of proper therapy [12] [13].

Factor X is a coagulation factor, dependent on vitamin K and its important role in the coagulation cascade cannot be overemphasized. Amongst all inherited coagulation disorders, hereditary factor X deficiency is quite rare with an incidence of 1 in 1 million. It is transmitted in an autosomal recessive fashion and clinically presents in a variety of ways, with heterozygotes being asymptomatic while the homozygotes show a multitude of bleeding manifestations.

The factor X gene is found on the long arm of chromosome 13, in close proximity to the gene for factor VII. This gene is quite similar in structure and chemical composition to the genes encoding for the other vitamin-K-dependent factors, thereby hinting at a common origin. Eight exons are found in this gene, with every exon coding for a specific functional protein domain in the gene product.

A large number of mutations have been described in the factor X gene, some of which include Gly366Ser, Arg347His, Phe31Ser, Gly133Arg, Val196Met, Gly204Arg, Glu51Lys, and Cys364Arg. Some cases have shown mutations in the GLA-domain of factor X, a component of its light chain [2] [3] [4]. A glutamine-to-glycine mutation has also been described at residue 32, affecting the gamma-carboxylation of factor X. Substitutions of serine with proline in exon VIII affect the cleavage site of factor X, thus preventing its activation.

A natural variant of factor X, with a deletion of Asp-185, may only show mild degrees of bleeding even in cases of severe deficiency [5].

The incidence of hereditary factor X deficiency is extremely low, with only about 50 cases reported worldwide [6]. The homozygous form of this disease occurs in about 1:500,000 – 1,000,000 of the general population, while the subtler heterozygous (carrier) form is far more prevalent with a rate of 1:500 [7] [8]. In countries like Italy and the UK, it is reported to affect about 0.4-0.5% of the general population. In contrast, in countries like Iran where consanguineous relationships are prevalent, it accounts for 1.3% of all hereditary coagulation disorders, with a high prevalence of 1: 200,000 population [9].

FX plays a central role in the blood coagulation cascade. FX forms a connection between the extrinsic and intrinsic pathways of coagulation through the “common pathway” that leads to thrombus formation. FX is activated by FIXa and FVIIIa (in the intrinsic pathway) and FVIIa (in the extrinsic pathway). This activated FX then converts prothrombin to thrombin in the presence of FVa, calcium ions, and phospholipids. A deficiency of FX will thus, block the formation of thrombin (and hence, the conversion of fibrinogen to fibrin) and the patient presents with a multitude of bleeding manifestations.

FXa is inactivated by antithrombin; it forms a complex with it that is rapidly cleared from the circulation. FX is produced in the liver with concentrations in the blood reaching 10 ug/ml [11].

Hereditary FX deficiency is a condition that lasts lifelong and the cornerstone of prevention is built on prophylactic treatment, education, and counseling. Prophylactic therapy is needed to prevent life-threatening episodes of bleeding, especially in patients with genotypes associated with an increased risk of hemorrhage. Carriers, diagnosed during routine blood tests, need to be counseled on the future risk of hemorrhage, especially in times of hemodynamic stress like surgeries, trauma etc. Pregnant women may need specialized care in hemophilia centers.

Hereditary factor X (FX) deficiency, also known as inherited factor X deficiency is a rare disease found mostly in communities where consanguinity is prevalent. It affects all age groups and both the sexes. Reported as far back as 1950 during a study conducted on patients who had some hemorrhagic disease, this disorder is also called Stuart and Prower factor deficiency owing to the fact that they were the first patients in whom the disease was first discovered.

It is inherited in an autosomal recessive fashion and manifests as a variety of bleeding disorders ranging from mild mucocutaneous bleeding to severe bleeding leading to exsanguination postoperatively, hemarthrosis and menorrhagia [1]. Newborns can present with severe umbilical stump bleeding and excessive bleeding post circumcision. Intracranial hemorrhage has also been reported, with fatal consequences.

In homozygous patients, the presentation is severe, while heterozygous patients are mostly asymptomatic, only showing symptoms in conditions of severe hemodynamic instability.

The treatment of this disorder is aimed at providing the body with activated vitamin K dependent factors through transfusion of fresh frozen plasma (FFP) or protein cell concentrate (PCC).

Hereditary factor X (FX) deficiency is an inherited bleeding disorder characterized by the deficiency of a coagulation factor named factor X. This deficiency predisposes the individual to an increased risk of bleeding.

It is a rare disease affecting both sexes and may present at any age. The condition is caused by a mutation in the gene responsible for controlling the production of plasma FX. The severity of bleeding is directly proportional to the FX levels in the blood.

Carriers are usually asymptomatic. Patients may present with a variety of bleeding manifestations that include severe bleeds following surgery, recurrent nosebleeds, soft tissue bleeds, excessive menstrual bleeds, blood in the urine, joints etc. It may also present with severe life-threatening bleeding in infancy.

Many are diagnosed based on a positive family history, or when they have abnormal clotting profiles that include elevated prothrombin time (PT) and activated partial thromboplastin time (APTT). Prolonged PT, APTT and Russel viper venom (RVV) times, and low levels of factor FX are the cornerstone for diagnosis.

There is no specific treatment available but prothrombin cell concentrates and fresh frozen plasma may be given to replace factor X directly. Such therapies help to reduce bleeding episodes and decrease the mortality of this disease. The outcome of hereditary FX deficiency is thus, dependent on prompt and early diagnosis and treatment.

1. Mannucci PM, Duga S, Peyvandi F. Recessively inherited coagulation disorders. Blood. 2004;104:1243–1252.
2. Girolami A, Allemand E, Scandellari R, Lombardi AM, Girolami B. The clinical and laboratory significance of cases of congenital FX deficiency due to defects in the Gla-domain. Hematology. 2009;14(3):177-81.
3. Isshiki I, Favier R, Moriki T, et al. Genetic analysis of hereditary factor X deficiency in a French patient of Sri Lankan ancestry: in vitro expression study identified Gly366Ser substitution as the molecular basis of the dysfunctional factor X. Blood Coagul Fibrinolysis. 2005;16(1):9-16.
4. Wang WB, Fu QH, Zhou RF, et al. Molecular characterization of two novel mutations causing factor X deficiency in a Chinese pedigree. Haemophilia. 2005;11(1):31-7.
5. Lu Q, Yang L, Manithody C, Wang X, Rezaie AR. Molecular basis of the clotting defect in a bleeding patient missing the Asp-185 codon in the factor X gene. Thromb Res. 2014 Nov;134(5):1103-9. doi: 10.1016/j.thromres.2014.08.004.
6. Roberts HR, Escobar MA. Inherited disorders of prothrombin conversion. In: Colman RW, Marder VJ, Clowes AW, Geroge JN, Goldhaber SZ, eds. Hemostasis and thrombosis — Basic principles and clinical practice. 5th ed. Lippincott Williams & Wilkins; Philadelphia,PA;2006; 923–937.
7. Peyvandi F, Duga S, Akhavan S, Mannucci PM. Rare coagulation deficiencies. Haemophilia 2002; 8: 308–21.
8. Graham JB, Barrow EM, Hougie C. Stuart clotting defect. II. Genetic aspects of a “new” hemorrhagic state. J Clin Invest 1956; 36: 497–503.
9. Karimi M, Yarmohammadi H, Ardeshiri R, Yarmohammadi H. Inherited coagulation disorders in southern Iran. Haemophilia 2002; 8: 740–4.
10. Pfeiffer RA, Ott R, Gilgenkrantz S, Alexandre P. Deficiency of coagulation factors vii and x associated with deletion of a chromosome 13 (q34). Evidence from two cases with 46,xy,t(13;y)(q11;q34) Hum Genet.1982;62:358–360.
11. Bajaj SP, Mann KG. Simultaneous purification of bovine prothrombin and factor x. Activation of prothrombin by trypsin-activated factor x. J Biol Chem. 1973;248:7729–7741.
12. Citak A, Ucsel R, Karabocuoglu M, Unuvar A, Uzel N. A rare cause of intracranial hemorrhage: factor X deficiency. Pediatr Emerg Care. 2001 Oct. 17;(5):349-50.
13. Young TM, Chitnavis BP, Swallow EB, Arya R, Vadher BD. Intracerebral hemorrhage in an adult due to transient factor X deficiency. J R Soc Med. 2003 Jul. 96; (7):355-6.
14. Kumar A, Mishra KL, Mishra D. Hereditary coagulation factor x deficiency. Indian Pediatr.2005;42:1240–1242.
15. Acharya SS, Coughlin A, DiMichele DM, T.N.A.R.B.D.S. Group. Rare Bleeding Disorder Registry: deficiencies of factors II, V, VII, X, XIII, fibrinogen, and dysfibrinogenemias. J Thromb Haemost 2003; 2: 248–56.