Full text in pdf format

Estimation of genetic risks of carriership for possible carriers of christmas disease (hemophilia b) ^*

N. Ferrari^I; C.R. Rizza^II

^IDepartamento de Biologia, Universidade Federal de Santa Catarina, 88000 Florianópolis, SC, Brasil. Send correspondence to N.F.
^IIOxford Haemophilia Centre, Churchill Hospital, Oxford, OX3 7LJ, England

ABSTRACT

Haemophilia B, or Christmas disease, is a genetic bleeding disorder due to a congenital deficiency of factor IX coagulant activity. It is inherited as a sex-linked recessive characteristic. The recurrence risk for the mother or sister of a sporadic case depend- on the incidence of carriers in the population, which can be calculated when the mutation rate of the gene and the reproductive fitness of affected males are known. The reproductive fitness calculated in this paper was of 0.53; the proportion of affected males in England and Wales was of 2 x 10^-5, the mutation rate for the gene was of 0.31 x 10⁵ and the incidence of carriers was of 3.4 x 10-5.
The probability of carriership obtained for mothers of sporadic cases was of 0.83, and for sisters of sporadic cases was of 0.41.

Keywords: genetic risks; christmas disease; hemophilia b.

REFERENCES

Barrai, I., Carr, H.M., Cavalli-Sforza, L.L. and de Nicola, P. (1968). The effect of parental age on rates of mutation for hemophilia and evidence for differing mutation rates of hemophilia A and B. Am. J. Hum. Genet. 20: 175-196.

Haldane, J.B.S. (1935). The rate of spontaneous mutation of a human gene. J. Genet. 31: 317-326.

Murphy, E.A. and Chase, G.A. (1975). Principles of Genetic Counselling. Year Book Medical Publishers, Chicago.

Rizza, C.R. and Spooner, R.J.D. (1983). Treatment of haemophilia and related disorders in Britain and Northern Ireland during 1976-80: a report on behalf of the Directors of Haemophilia Centres in the United Kingdom. Br. Med. J. 286: 929-933.

Werner, B. (1983). Conference of Regional Health Authority Statisticians - Harrogate (N.H.S. Training Centre).

* Part of the Ph.D. Thesis presented by N.F. to the Oxford Haemophilia Centre, Oxford, England