In the early days of the semiconductor industry, hermetically packaged transistors and integrated circuits were randomly failing in the field for reasons not understood. The problem was eventually found to be the formation of a gold-aluminium intermetallic compound where gold wires were bonded to aluminium pads on chips. This ceramic-like substance is purple in colour, and was dubbed the “purple plague”. The problem was solved by using low-temperature bonding techniques to avoid formation of the compound or avoiding aluminium to gold junctions entirely.
A purple plague-like scenario was used by Larry Niven in Ringworld to explain the collapse of the technological civilisation of the engineers who built the megastructure. Their technological tools were attacked by a contagious plague, and could not be rebuilt without the tools themselves that the plague destroyed.