Molecular diagnosis in haemophilia A.

Haemophilia A is the commonest cause of X-linked inherited bleeding disorder. Due to inadequate medical facility for management of the disease, the DNA based genetic diagnosis has assumed great importance. Ideally, the direct detection of mutations is the most accurate and reliable approach for carrier detection and prenatal diagnosis. However, mutation detection is possible only in limited number of cases. In majority of haemophiliacs, no common mutation is easily identifiable. The limitation has been over come by the use of linkage-based analysis using polymorphic DNA markers in the factor VIII gene. Some of these markers can be identified by restriction enzymes and are called RFLP markers. Other markers are a class of short tandem repeats sequences which result in differences in the number of CA repeats in different individuals. The combined use of these markers has made it possible to identify carriers and provide prenatal diagnosis in upto 95% of families having affected individuals. Therefore, the recurrence of the disease can be prevented to a great extent in the haemophilia A affected families.