Patient A suffers from Down syndrome. This is a genetic disease that occurs when there is a trisomy (triplication) of the 21st chromosome. Only a small portion of the chromosome needs to be triplicated to get the effects of Down syndrome. It was discovered by John Lagdon Down in 1866, as he studied children with mental retardation in Surrey, England. Down was the superintendent for an asylum when he began his study. Later on, during the late 1950's, the syndrome was associated with the 21st chromosome.
In 1959, Jerome Lejeune and Patricia Jacobs first determined the cause of Down syndrome to be the extra chromosome in the 21st pair. This spawned the separation of Down into translocation and mosaicism. Translocation is also known as Robertsonian Translocation. This defines the process by which two breaks occur in separate chromosomes, usually the 14th and 21st. Through rearrangement, the 14th chromosome is then replaced by an extra 21st, which leads to Down syndrome.
The other cause is known as mosaicism. This is seen as people having a mixture of cell lines, some normal, and some that have trisomy 21 (Down syndrome). The way this works, a patient may have normal blood cells, but their skin cells will have trisomy 21, leaving them with Down syndrome.
Down syndrome is a life long disease that does not reccess. Although it is difficult to deal with, many adult patients work in a tightly structured job and live in group homes. This allows for some growth and development, but it is still minimal. Scientists continue to look for a cure, but have still yet to find one. Although the process is slow, they still hope to discover one soon, and progress is being made, especially after they found out the associations with the 21st chromosomes. But there is still no cure.