I'm trying to build a designer organism that would prove a threat to all life on Earth. Sort of a semi-organic von Neumann ecology of microscopic nitrogen-eaters that rapidly consume nitrogen to fuel their own growth, which not only threatens to drastically accelerate the depletion of Titan's nitrogen atmosphere (which millions of off-world human colonies need to grow food) but also disrupt the nitrogen cycle that's vital to all life on Earth, killing all Earth-born life wherever it goes.
To this end, if I want my organism to have the kind of properties I've just described, then I need to know what happens if it enters a human body and starts living in there by cannibalizing its nitrogen content. What might happen to a person who rapidly loses their normal bodily concentration of nitrogen, dropping from say 3% to 1% or lower?