PARTIAL bone marrow transplants may largely cure sickle cell anaemia without
many of the risks associated with complete marrow transplants.
The disease, common in people from tropical regions, is caused by faulty
genes for the red blood pigment haemoglobin. Sufferers have many rigid and
misshapen red blood cells that can obstruct blood flow, causing severe
pain and damaging organs.
Trials carried out in the past decade have shown that completely destroying
patients鈥� bone marrow鈥攖he tissue that produces red blood cells鈥攁nd
replacing it with normal donor marrow can cure the disease. But this is
extremely risky.
Advertisement
If the body rejects the new marrow, for example, the patient has no marrow
left at all. One in ten people die after this treatment, so it is justified only
for the severest forms of sickle cell anaemia.
But if you replace only part of the marrow, people can survive even if the
transplant fails, says Robert Iannone, a haematologist at Johns Hopkins
University in Baltimore. His team carried out trials in mice that showed that
replacing as little as 25 per cent of their bone marrow meant that 90 per cent
of the red blood cells were normal (Blood, vol 97, p 3960). 鈥淲ith 40 per cent
donor marrow, there was no evidence at all of sickle cells,鈥� Iannone says.
His team has already begun trials of the technique in humans. The two
patients treated so far are doing well, he says.
A number of other centres are also starting partial transplantation trials on
people, says Ann Woolfrey, a researcher at the Fred Hutchinson Cancer Research
Center in Seattle. 鈥淚t鈥檚 very much a hot topic,鈥� she says.
However, it may not be a complete cure. Even small numbers of sickle cells
continue to create some problems in mice. The risk of the transplanted marrow
attacking the host鈥檚 body remains. And partial transplant patients may have to
take immunosuppressant drugs for the rest of their lives, although Iannone hopes
this won鈥檛 be necessary. But the researchers point out that this is preferable
to regular trips to hospital for blood transfusions.