Genetic screening: ethical issues - Nuffield Council on Bioethics
Genetic screening: ethical issues - Nuffield Council on Bioethics
Genetic screening: ethical issues - Nuffield Council on Bioethics
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113<br />
Polycystic kidney disease<br />
Mode of inheritance : recessive (infantile form)<br />
dominant (adult form)<br />
There are several disorders in which cysts occur in the kidneys. Two main inherited<br />
types can be distinguished. Infantile polycystic kidney disease is present at birth. It<br />
is inherited in a recessive manner and can be detected before birth by ultrasound.<br />
Adult polycystic kidney disease is a comm<strong>on</strong> dominantly inherited disorder, with a<br />
worldwide prevalence of between 1 in 500 and 1 in 1,000 individuals. Symptoms do<br />
not usually appear until around 40 years of age. Small cysts may be detected before<br />
birth by ultrasound examinati<strong>on</strong>; they enlarge slowly throughout life but <strong>on</strong>ly about 50%<br />
of affected individuals will develop severe kidney failure by age 70.<br />
Rhesus haemolytic disease<br />
Rhesus haemolytic disease can occur if the mother’s blood group is rhesus negative<br />
and the father’s is rhesus positive (about 85% of people are rhesus positive and 15%<br />
are rhesus negative). In this situati<strong>on</strong>, the fetus may also be rhesus positive. If<br />
sufficient leakage of fetal blood into the maternal circulati<strong>on</strong> occurs, which is particularly<br />
likely at the time of delivery, a rhesus negative woman can develop antibodies against<br />
the rhesus positive blood group and subsequent babies may be affected, with<br />
destructi<strong>on</strong> of their red blood cells causing anaemia and jaundice. Very severely<br />
affected infants have problems before birth; after birth treatment (exchange transfusi<strong>on</strong>)<br />
may be needed to correct anaemia and prevent brain damage due to jaundice.<br />
The c<strong>on</strong>diti<strong>on</strong> used to cause 1-2/1,000 stillbirths or deaths in the newborn period. It<br />
is now largely prevented by <str<strong>on</strong>g>screening</str<strong>on</strong>g> all pregnant women for their rhesus blood group<br />
early in pregnancy and ensuring that all are given an injecti<strong>on</strong> of antibody within a few<br />
hours of delivery (or miscarriage). This removes any fetal rhesus positive cells from<br />
the mother’s bloodstream and so prevents her becoming immunised in almost every<br />
case.<br />
Rubella (German measles)<br />
Mode of inheritance : not inherited - a virus causing c<strong>on</strong>genital malformati<strong>on</strong>s<br />
If rubella is c<strong>on</strong>tracted in the early stages of pregnancy (before about 12 weeks) it can<br />
cause stillbirth or serious c<strong>on</strong>genital malformati<strong>on</strong>s such as blindness, deafness, heart<br />
defects and mental retardati<strong>on</strong>. As a result of programmes both for immunising<br />
schoolgirls and n<strong>on</strong>-pregnant women against the virus, and by <str<strong>on</strong>g>screening</str<strong>on</strong>g> during<br />
pregnancy, the incidence of children born with severe c<strong>on</strong>genital rubella syndromes has<br />
declined from about 3.5 to 0.41/100,000 births between 1980 and 1985 in most of<br />
Western Europe.<br />
Sickle cell disease - see Haemoglobin disorders