Question

Which of the following diseases is also called Christmas disease?
A. Sickle cell anaemia
B. Hemoglobinuria
C. Myocardial infarction
D. Haemophilia B

Answer 1

Hint: It is a blood clotting disorder caused due to an inherited mutation of the gene for factor 9. It is a disorder that is present in the Royal family of England.

Complete answer: Haemophilia B, also called Christmas disease, is a genetic disorder that occurs due to inherited mutation of the gene for factor 9, i.e. a clotting protein. It is less common than Haemophilia A. Out of the two sex chromosomes, i.e. X and Y chromosomes, the gene for haemophilia is present on the X chromosome. It is passed on to the progeny through the X chromosome. Since females have two X chromosomes, they act as carriers for the disease. Male progeny inherits an X chromosome from their mother and Y chromosome from their father. Therefore, if the male inherits mutated X-chromosome, then the male inherits the disease. Haemophilia rarely occurs in females. however, she can pass the gene onto the progeny. The mutated X chromosome causes internal bleeding from the muscles and joints or external bleeding from the minor cuts. Since the blood clotting factor is absent because of a mutated gene, therefore the affected person bleeds longer than other people. Such profuse bleeding may have fatal consequences.
Hence, the correct answer is option D.

Note: Normal plasma levels of F9 range from 50%-150%. Plasma level below this range gives an estimate of a person’s symptoms. Based on the plasma level range, haemophilia is categorised as:
a. Mild haemophilia B (6%-48%)
b. Moderate haemophilia B (1%-5%)
c. Severe haemophilia B (below 1%)