ul th ood . ▁Mut ated ▁alle les ▁are ▁inherited ▁in ▁aut os om al ▁dominant ▁fashion , ▁although ▁de ▁nov o ▁mut ations ▁can ▁also ▁cause ▁sp or adic ▁emer gence ▁of ▁dise ases . ▁The ▁age ▁of ▁on set ▁and ▁sever ity ▁vary ▁significantly ▁among ▁patients ▁with ▁SF TP C ▁mut ations , ▁some ▁only ▁manifest ▁sympt oms ▁in ▁fifth ▁or ▁sixth ▁de cade . ▁Most ▁of ▁these ▁mut ations ▁are ▁miss ense , ▁but ▁there ▁have ▁been ▁record ings ▁of ▁frames h ift , ▁sp lice - site ▁mut ations , ▁together ▁with ▁small ▁insert ions ▁or ▁delet ions ▁along ▁the ▁car box yl ▁terminal ▁of ▁SF TP C . ▁Mut ations ▁in ▁SF TP C ▁gene ▁are ▁thought ▁to ▁prevent ▁pro SP - C ▁pe pt ides ▁from ▁being ▁fully ▁processed ▁into ▁m ature ▁SP - C ▁prote ins . ▁Pro SP - C ▁prote ins ▁tend ▁to ▁self - acc um ulate ▁along ▁the ▁secret ory ▁path way , ▁due ▁to ▁high ▁hydro ph ob ic ▁nature , ▁and ▁may ▁activ ate ▁cell ular ▁destruction ▁response . ▁SF TP C ▁mut ations ▁cause ▁pro SP - C ▁prote ins ▁to ▁aggregate ▁and ▁mis fold ▁during ▁secret ory ▁process . ▁These ▁fol ded ▁prote ins ▁trigger ▁unfold ed ▁protein ▁response ▁( UP R ) ▁and ▁cell ular ▁apo pt osis ▁to ▁get ▁rid ▁of ▁clusters ▁of ▁mut ated ▁pe pt ides . ▁Pat ients ▁with ▁SP - C ▁d ys function ▁show ▁lack ▁of ▁m ature ▁SP - C