Intelligence, howsoever one measures it, varies from person to person. It is thought that the variation in intelligence in Bloom's syndrome, as a matter of averages, is a little towards the lesser. But intelligence is a dynamic process, nurtured by many environmental cues and guided by inherent neurologic factors. Persons with Bloom's syndrome generally do not develop the normal range of interests, and they lack an appetite for school learning. There is a deficit in capacity for abstract thought.
Could these problems with school learning and bated interests in stimulating activities be related to the development of the nervous system in the brain? If we think that it does, how does the development of the brain in Bloom's syndrome result in these distal capacities? Can we effectively compensate for the deficits and, if so, what is the most robust way to do this?
Most cells in the nervous system are terminally differentiated, which means that they have reached their final cell fate and are not able to divide. Consequently, stem cell* populations play a more limited role in maintaining organ function in the brain. But rapid cell proliferation during fetal development is essential to establish the numbers of cells that make up the adult brain, and normal maintenance of brain nerve cells can be compromised by poor DNA repair, an outcome we have learned from a number of different human syndromes that have defects in DNA repair.
The brain in persons with Bloom's syndrome is smaller than expected based on size. Within the normal range of human brain sizes, there is no direct relationship between brain size and intelligence. However, a very small brain certainly can limit a person's intelligence and lead to mental delays. Are the intelligence factors discussed above related to the size of the brain?
The smaller size of the brain could be a consequence of the proliferative defect that pervades all aspects of development in Bloom's syndrome. On the whole, the cognitive and psychological effects of the abnormal brain development in Bloom's syndrome have not been well studied and are not understood. These studies could be centrally important for persons with Bloom's syndrome because mental function and quality of life are tied so closely together. We should learn more about them to compensate and remediate in the best way possible to achieve the best quality of life possible.
*For more information about stem cells, please see Small Body Size.