HEALTH / Second opinion

THE PAST 20 years have seen rapid advances in scientific knowledge about inherited disorders: the individual genes responsible for hundreds of diseases have been isolated, and the precise mechanisms identified. For many families blighted by an inherited disease, however, the first practical effect has been only that they can be offered diagnosis before birth. If the foetus is affected the pregnancy can be terminated.

For a few disorders this draconian approach is now being softened by the development of better treatments, offering an alternative to parents who are not prepared to consider selective abortion. Indeed, families affected by genetic disorders are beginning to be faced with a complex array of choices, with the outlook and the options changing every few years.

Thalassaemia is an example. This potentially fatal blood disorder was one of the first conditions for which genetic diagnosis became possible, allowing people at risk to discover if they carried the defective gene and giving them the option of selective termin-ation of pregnancies. Thalassaemia is common in Italians, Cypriots and Greeks (its name comes from the Greek word for the sea) and is also found in Arabs, Asians and Africans. In parts of Italy 10 per cent of the population have one of the abnormal genes, so that one couple in every 100 risks having children with the disorder. An affected child becomes sick within a few months of birth. The blood cells contain a faulty form of the red pigment haemoglobin, and the child becomes pale, jaundiced, weak and breathless and its growth is stunted. Without treatment few children survive to adult life.

Genetic screening and termination of affected pregnancies has led to substantial reductions in the numbers of children being born with the disease in Cyprus, Sardinia and other Mediterranean countries and also in the Cypriot community in London, but around the world most couples at risk discover that they have faulty genes only when their child becomes sick.

Treatment is now possible - for those who can afford it.

Replacement of the defective red blood cells by transfusions from healthy blood donors will relieve the symptoms, but the iron in the transfused blood slowly accumulates and damages the heart and other organs. This build up of iron can be prevented by treatment with a drug, desferrioxamine, which has to be given by slow injection overnight for at least five nights every week.

People with thalassaemia who stick to the treatment - a transfusion every three weeks or so, desferrioxamine most nights, are maintained in reasonably normal health: a recent report in the New England Journal of Medicine described 97 people born with thalassaemia between 1954 and 1975 and treated in this way: 59 of the 97 were still healthy after 15 years or more of treatment. This approach has now been proved effective long term - but it is very demanding.

There is another treatment that offers the chance of a long-term cure for the disease: a bone marrow transplant. This possibility is, however, available in practice only to the 20 per cent or so of people with thalassaemia who have healthy siblings with matching bone marrow. The chances of cure are around 90 per cent but the operation carries a risk of 3-5 per cent of death from complications.

These life-saving treatments are extremely expensive: the cost in the US of treatment by transfusions and desferrioxamine is about dollars 30,000 (around pounds 19,500) a year for life, while a bone marrow transplant costs dollars 170,000 (pounds 110,000). In most of the countries in which thalassaemia is common, medical facilities for these treatments are available to very few people, or not at all, and the costs are prohibitive.

For such societies the screening/ selective abortion policy will remain the only practical answer for the foreseeable future - further evidence of the yawning gap between the world's haves and have nots.