I didn't know I had MGUS, until I was diagnosed with PN. I was told it was about the size of a freckle, and in past three years, it hasn't grown. My doctor told me that there are many people running around that may have this disorder, and just don't know it, because they aren't typically tested for this malady. It is a pre-cancerous condition that can lead to multiple myeloma. So, one does need to be tested on an annual basis. However, it doesn't necessarily lead to MM. It is a minor concern, but mine hasn't changed in size, and that is a relief.