This part deals with the existing and possible future cures for CNS.
E1. IS THERE A CURE FOR CNS?
As at mid 2006, the only known cure for CNS is a liver transplant. This is a very serious surgical operation that, because of the possibility of rejection of the implanted liver, is followed by the use of immunosuppressant drugs while the “foreign” liver is in place. Immunosuppressant drugs render the patient more vulnerable to a range of other illnesses. Liver transplants are not always successful, but many are. Surgical success rates are improving, as are immunosuppressant drugs.
With a total liver transplant the original liver is removed and replaced by a donor liver. At present immunosuppressant drugs must continue for life, even if there is developed another cure for CNS. (See Question E4 concerning partial liver transplants.)
Whether and when a person with CNS should have a liver transplant has been a matter of some differences of opinion among the medical community.
E2. SHOULD CRIGLER NAJJAR PATIENTS HAVE A LIVER TRANSPLANT?
Generally, liver transplants are not performed on very small babies. In order to hold a child safe there is therefore always a need to institute treatment and management of the condition for a number of years. This gives an opportunity to assess the effectiveness of treatments and the lifestyle implications.
It is relevant to recall that until about 35 years ago most people with CNS died in infancy. Many people with CNS, who have been kept safe by phototherapy, are now reaching late teens or adulthood when intensive phototherapy has an even greater impact on lifestyle. Unless an alternative cure is found, the option whether or not to have a liver transplant becomes a major and difficult decision, particularly for the most serious CNS cases.
Whether a transplant or ongoing treatment is the preferred course depends, among other things, on:
The issue of whether to manage the condition or have a transplant requires very careful consultation between people with CNS, their carers, clinicians and surgeons.
E3. WHEN IS THE BEST TIME FOR A LIVER TRANSPLANT?
Subject to there being available a donor liver, a liver transplant is possible throughout life. It is usually considered that there are two good windows of opportunity. One is when a child is aged about 7 to 10 when one lobe of an adult donor liver is a suitable size for transplanting to the child. The second is when the person is (or is nearly) fully-grown.
In some countries the favoured approach is for children to have transplants when about 7 to 10. This is not an easy decision for parents. In the Netherlands, where well-informed and disciplined treatment is usually available, the preference is, where possible, to wait until late teens. This allows the person with CNS to make his or her own decision between some lifestyle limitations due to phototherapy and a lifetime on immunosuppressant drugs.
E4. WHAT ARE THE BENEFITS OF A PARTIAL LIVER TRANSPLANT?
Instead of fully replacing a liver with a donor liver, it is possible to add a part of a donor liver to a patient's natural liver. Immunosuppressant drugs are still required to prevent rejection of the “foreign” liver tissue. One advantage of this procedure is that, if the body rejects the new partial liver, it can be removed and the natural liver remains to perform the many other liver functions.
If an alternative cure is subsequently developed, the foreign liver can be surgically removed and the immunosuppressant drugs needed to prevent its rejection can be dispensed with.
Partial liver transplants can be technically more difficult procedures than full transplants and thus may involve greater operating risk. Not all liver transplant surgical centres undertake partial liver transplants.
E5. WHAT ARE THE PROSPECTS FOR FUTURE CURES?
Some 5 years ago, hopes were high that gene therapy would soon provide a permanent cure for CNS (and many other conditions). There have been setbacks in the development of gene therapy and, while much research continues, the hopes for an early cure have faded somewhat.
The possibility of introducing a massive number of individual “foreign” liver cells into the liver to produce the enzyme has had a number of clinical trials. The procedure is much less invasive than a liver transplant. Immunosuppressant drugs are still required to prevent rejection of the “foreign” liver cells at least until an alternative cure is found. So far this procedure has not provided sufficient production of enzyme to make phototherapy unnecessary. This research is still in its infancy.
Because of the rarity of CNS, research into specific cures for the condition is limited. The possibility exists that a cure may emerge as a spin-off from research into other more common conditions. Stem cell research is one such area.
For a child born today with CNS the knowledge exists to hold the child safe using phenobarbital or phototherapy for at least 15 years. In that time: