My son was diagnosed with an immune deficiency because he was literally non stop sick. Then he started getting serious illnesses like pneumonia and osteomylitis. Blood tests were run, the first test was a pneumovac shot and the blood tests to check his immune responce to the shot. He had none. To find information and a list of the 10 warning signs of immunodeficiency just search "primary immune deficiencies" on your web browser. You should find lots of information. The immune deficiency my son has is DiGeorge Syndrome. However there are over 80 different kinds, IgG subclass def. being one of them, as well as IgA def., common variable def., SCID (severe combined), hyper IgM etc... getting diagnosed is not easy. It took us 4 years to get a begining diagnosis of IgG sub. def., and only just last year the diagnosis of DiGeorge. It isn't an easy road for answers but keep looking and searching. Half the battle is just to know how to search and what to search for.