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     Blood Related Disorders:

 

  Haemophilia

Haemophilia is group of sex linked recessive disorders that impair the body's ability to control blood clotting or coagulation, which is used to stop bleeding when a blood vessel is broken. Haemophilia A (clotting factor VIII deficiency; MIM: 306700) is the most common form of the disorder, occurring at about 1 in 5,000 to 10,000 male births. Haemophilia B (factor IX deficiency; MIM: 306900) occurs at about 1 in about 20,000-34,000 male births, with no significant racial difference. They are clinically almost identical and are associated with spontaneous bleeding into joints and muscles and internal or external bleeding after injury or surgery. Both the conditions are X-linked and virtually all sufferers of hemophilia are males. Female carriers may also bleed abnormally, because some have low levels of the relevant clotting factor. Other deficiencies of coagulation factors that cause a bleeding disorder, such as afibrinogenaemia, hypoprothrombinaemia, deficiencies of factor V, combined factor V and factor VIII, factor VII, factor X, factor XI, and factor XIII, are inherited as autosomal recessive traits and are generally much rarer than the hemophilias, with prevalence in the general population varying between 1:500,000 and 1:2,000,000. Apart from these, one of the most common heridetary coagulation disorder is known as Von Willebrand disease, is inherited as autosomanl dominant pattern. The birth rate haemophilia in India is 32 per 1,000 births.

  Thalassemia

Thalassemia is a blood related disorder that is mostly transmitted in autosomal recessive mode. In thalassemia, the genetic defect results in reduced rate of synthesis of one of the globin chains that make up hemoglobin leading to the formation of abnormal hemoglobin molecules, thus causing anemia, the characteristic presenting symptom of the thalassemias. The disease is particularly prevalent among Mediterranean people (especially among the Greeks). The thalassemias are classified according to which chain of the hemoglobin molecule is affected. In alpha thalassemias ( MIM: 141750  and  MIM: 301040), production of alpha globin chain is affected, while in beta thalassemia ( MIM: 603902) production of beta globin chain is affected. alpha thalassemias primarily involve the genes HBA1and HBA2, beta thalassemias are due to mutations in the HBB gene. It involves decreased production of normal adult hemoglobin, the predominant type of hemoglobin from soon after birth until death. There are two forms of beta thalassemia: thalassemia minor and thalassemia major (which is also called Cooley's anemia). There are an estimated 60-80 million people in the world who carry the beta thalassemia trait. People who carry thalassemia in India alone number approximately 30 million.  In India , beta thalassemia is very common in the north eastern region with a frequency of 7-64%. High frequency of beta thalassemia trait is also reported in Gujarat, Punjab, Tamil Nadu and West Bengal.

                 Considering the preponderance of diagnosed thalassemias over a thalassemias, this database presently holds the relevant data for thalassemias only.

  Glanzmann Thrombasthenia

Glanzmann thrombasthenia is a bleeding disorder characterized by failure of platelet aggregation and by absent or diminished clot retraction. It can be inherited in an autosomal recessive manner ( MIM: 273800) or autosomal dominant manner ( MIM: 187800). The recessive disease results from mutations in either the gene encoding platelet glycoprotein GPIIb (ITGA2B) or GPIIIa (ITGB3) genes.

            The database currently holds the relevant data for the autosomal recessive forms of Glanzmann thrombasthenia.

  Hermansky-Pudlak Syndrome

It is a rare autosomal recessive disorder characterised by oculocutaneous albinism, bleeding, and lysosomal ceroid storage result from defects of multiple cytoplasmic organelles: melanosomes, platelet-dense granules, and lysosomes. Hermansky-Pudlak syndrome (HPS) can be caused by mutation in several genes: HPS1 ( MIM: 604982), HPS3 ( MIM: 606118), HPS4 ( MIM: 606682), HPS5 ( MIM: 607521), and HPS6 ( MIM: 607522). HPS2 ( MIM: 608233), AP3B1 ( MIM: 603401), DTNBP1 ( MIM: 607145) and BLOC1S3 ( MIM: 609762).

The database presently holds the data for HPS1 and HPS9 only.

  Megaloblastic Anemia ( MIM: 249270)

TRMA is inherited in an autosomal recessive manner. The disorder is caused by a defect in a thiamine transporter protein, SLC19A2.

  Purpura ( MIM: 612304)

This autosomal recessive protein C deficiency resulting from homozygous or compound heterozygous PROC mutations is a thrombotic condition that can manifest as a severe neonatal disorder or as a milder disorder with late-onset thrombophilia; it is a haemorrhagic condition usually associated with sepsis or previous infection. It occurs mainly in babies and small children.

  Hypofibrinogenemia

Hypofibrinogenemia is a condition characterized by decreased levels of fibrinogen in the blood, caused by mutations in FGB gene mapped to 4q28 (  MIM: 202400). Patients suffer from bleeding problems that vary from mild to severe, depending upon the residual amount of fibrinogen in plasma.

  Venous thrombosis 

Venous thrombosis is characterized by abnormal formation of blood clot (thrombus) within a vein, influenced by both genetic and environmental influences. It mainly affects the large veins in the lower leg and thigh. The risk of venous thrombosis increases with age.

Mutation in the JAK2 gene ( MIM: 147796) is a common genetic cause of venous thrombosis.

  Dyskeratosis congenita ( MIM: 305000)

The disease mainly affects the integumentary system with a major consequence being anomalies of the bone marrow. The disorder is characterised by premature aging with cutaneous pigmentation, dystrophy of the nails, leukoplakia of the oral mucosa, continuous lacrimation due to atresia of the lacrimal ducts, often thrombocytopenia, anemia, and in most cases testicular atrophy. Only males are affected in a pattern consistent with X-linked recessive inheritance as a result of one or more mutations in the long arm of the X chromosome in the gene DKC1. This may result in specific issues related to dysfunctional rRNA and perhaps a graver phenotype.

  Factor V deficiency ( MIM: 227400)

Factor V deficiency is a rare autosomal recessive coagulation disorder caused by mutations in the F5 gene ( MIM: 612309).