Unsupervised Learning: What's in a name?

Unsupervised learning doesn't get all the attention that supervised learning does. However, unsupervised learning can often not only reveal patterns in data, but it can also be used to label data for supervised algorithms. Why are articles about rare diseases difficult to find in databases? Here, we can see that articles are grouped by patho-physiological terms that describe a disease--SBMA. Because medical databases index on the title, rare diseases may be hard to find because the disease name is not often in the title and even if it were, there aren't as many articles about rare diseases. However, searching for the correct terms leads to better results.