There are four subtypes of IgG 1,2,3,and 4,IgG2
deficiency being the one that causes the most problems
in children especially if there is a simultaneous deficiency of IgA,to confuse stuff more there is four other types of immunoglobins other than IgG. There is also IgA,IgD,IgE and IgM,each having multiple subsets. So you can see why it's important to have someone who understands this stuff to treat it.