I can't really reference what question you're referring to in Destroyer since we probably have different editions, but from my understanding, I think it has to do with the structural lining of the larynx and trachea? I believe they're both lined with cilliated pseudostratified columnar epithelial tissue. Cilia is made out of microtubules arranged in a 9+2 array and they help "sweep" out the airways in the respiratory tract from mucus, pathogens, or other debris. It acts like a protective mechanism to prevent unwanted particles travelling into the lungs. Thus, if a person is born with this genetic defect producing microtubule abnormalities, then it probably affects that clearing function of the cilia.
Someone please correct me if I'm completely off base. I realize I never even saw that question in the Destroyer I have (2015) so I'm just spitballing ideas 😛 Was there not an explanation in the back of the book?