Haemophilia B Classification & external resources
Haemophilia B (also spelled Hemophilia B or Hæmophilia B) is a blood clotting disorder caused by a mutation of the Factor IX gene, leading to a deficiency of Factor IX. It is the second most common form of haemophilia, rarer than haemophilia A. It is sometimes called Christmas disease after Stephen Christmas, the first patient described with this disease. In addition, the first report of its identification was published in the Christmas edition of the  British Medical Journal.
Additional recommended knowledge
Treatment (bleeding prophylaxis) is by intravenous infusion of factor IX.
The factor IX gene is located on the
X chromosome (Xq27.1-q27.2). It is an X-linked recessive trait, which explains why, as in haemophilia A, only males are usually affected.
Factor IX deficiency leads to an increased propensity for
haemorrhage. This is in response to mild trauma or even spontaneously, such as in joints (haemarthrosis) or muscles.
^ Christmas' disease at Who Named It Biggs RA, Douglas AS, MacFarlane RG, Dacie JV, Pittney WR, Merskey C, O'Brien JR. ^ Christmas disease: a condition previously mistaken for haemophilia. Br Med J 1952;2:1378-1382. PMID 12997790. See also
Pathology: hematology (primarily C81-C96/200-208, D45-D47, D50-D77/280-289) WBCs ( hematological malignancy lymphoma, leukemia, multiple myeloma), myeloproliferative disease, myelodysplastic syndrome -cytosis ( Agranulocytosis, Leukocytosis, Lymphocytosis, Monocytosis) • -penia ( Lymphopenia, Neutropenia) RBCs/ anemia/ hemoglobinopathy nutritional anemia: Iron deficiency anemia, Plummer-Vinson syndrome, Megaloblastic anemia ( Pernicious anemia) hereditary hemolytic anemia: G6PD Deficiency, Thalassemia, Sickle-cell disease/trait, Hereditary spherocytosis, Hereditary elliptocytosis, Hereditary stomatocytosis
acquired hemolytic anemia: Autoimmune ( Warm), HUS, MAHA, PNH, PCH
aplastic anemia: Acquired PRCA, Diamond-Blackfan anemia, Fanconi anemia • Sideroblastic anemia • Hemochromatosis Coagulation/ platelets coagulopathy: DIC • Hemophilia ( A/VII, B/IX, C/XI, XIII) • Von Willebrand disease
Purpura: Henoch-Schönlein, ITP ( Evans syndrome), TTP
primary : hypercoagulable state Protein C deficiency -
Protein S deficiency - Antithrombin III deficiency - Antiphospholipid syndrome - Factor V Leiden
other hemorrhagic conditions: Bernard-Soulier syndrome - Glanzmann's thrombasthenia - Grey platelet syndrome Histiocytosis WHO-I Langerhans cell histiocytosis - non-Langerhans-cell histiocytosis/WHO-II (Juvenile xanthogranuloma, Hemophagocytic lymphohistiocytosis) - malignant histiocytic disorders/WHO-III ( Acute monocytic leukemia, Malignant histiocytosis, Erdheim-Chester disease) Other Asplenia/hyposplenism - Methemoglobinemia