Christmas factor (IX) defect in a case of haemorrhagic thrombocythaemia.

The mechanism of bleeding in haemorrhagic thrombocythaemia is obscure. Although by definition there is always a raised platelet count, the haemorrhagic episodes cannot be satisfactorily correlated with the level of the count. In fact, thrombocythaemia can exist without bleeding manifestations (Fanger, Cella, and Litchman, 1954). The most commonly occurring laboratory defect is an abnormal bleeding time, this being increased in approximately 50 % of cases (Hardisty and Wolff, 1955). The introduction of the thromboplastin generation test by Biggs and Douglas in 1953 provided a valuable method of investigation, and has been applied in many of the reported cases of haemorrhagic thrombocythaemia. Attention has, however, been focused mainly on the platelets, and the results have varied considerably. This paper presents details of a case of haemorrhagic thrombocythaemia showing a Christmas factor deficiency.