An 18 year old man gets into a car accident and requires blood transfusion. When he gets transfused with the first unit, he experiences anaphylaxis. He has never had a blood transfusion in the past, but testing shows IgG antibodies against IgA. The only other thing he notes is that as a child, he had recurrent upper and lower respiratory tract infections with bacteria like S. pneumoniae and H. influenza.
Challenge: What's the diagnosis here?