Hi. After MAC diagnosis, I had immunology tests, and discovered my IgG was low–below ref range. I was started on Hizentra weekly infusions about a year ago, which I administer myself subcutaneously, and now I test in normal range for IgG. HIzentra is IgG from pooled blood sources. I used to shiver a lot and had to take hot baths in afternoon to stop. Now the shivers have gone away. Docs don't pay any attention to my report of shivers, but nurses say lots of MAC patients have them. I also do not get as many Upper Respiratory infections. Note– I did not have terribly low IgG, and a second immunologist said she would not have prescribed the HIzentra. It has made my hair thinner (I blame it anyway). And it has goofed up an annual test I do which is a biomarker for a certain type of thyroid cancer because I now have thyroid antibodies — so I will go off Hizentra for a month to do the test.