Haemophilia
Haemophilia A is an X-linked, recessively inherited condition caused by a deficiency
of factor VIII. The degree of severity is very varied but tends to be consistent within
the same family. Children with over 25% of normal levels of circulating factor VIII
may lead normal lives, those with between 1% and 5% are moderately to severely
affected by minor trauma, etc., while those with under 1% have multiple bleeds into
joints (haemarthroses) and may be severely physically handicapped as a result.
Obviously, prevention of trauma to those who have this condition is extremely
important, but the availability of factor VIII concentrates has revolutionized the
quality of life of haemophiliacs. Unfortunately, some of these blood replacement
products have been contaminated in the past with hepatitis and human
immunodeficiency virus (HIV) and, therefore, cross-infection control is a high
priority. It was found that a number of patients who were thought to be haemophiliacs
did not respond to replacement with factor VIII (antihaemophiliac globulin) but were
deficient in another factor⎯factor IX. This is known as Christmas disease or
haemophilia B. This is also transmitted as an X-linked recessive trait with a wide
range of clinical severity, but female carriers of this condition also have a tendency to
bleed.
Key Points
Factor VIII level:
25%⎯mild;
- 1-5%⎯moderate to severe;
- <1%⎯severe.
Von Willebrand's disease
This is a dominantly inherited, complex, and variable condition characterized by a
vascular abnormality of large irregular capillaries, defective platelets that do not
adhere to each other, and decreased levels of factor VIII. Common clinical
manifestations are nose bleeds and spontaneous gingival haemorrhage. Von
Willebrand's disease is the most common inherited bleeding disorder affecting, ~1 in
every 1000 individuals in the United States and the United Kingdom.
Thrombocytopenia
This is caused by a reduction in the numbers of circulating platelets in the
bloodstream.
Normal levels are between 150 and 400 × 109 /l. The platelet count should be at least
50 × 109 /l before surgery is attempted. Clinical signs are petechial haemorrhages into
the skin and mucous membranes with haematemesis (blood in the vomit), haematuria
(blood in the urine), and melaena (blood in the faeces).
In children the usual causes of thrombocytopenia are idiopathic, an acute immune
response usually following an upper respiratory tract infection, leukaemic infiltration
of the bone marrow, or following the administration of various drugs.