A pre-existing condition seems to be something you cannot buy "insurance" for.
Insurance is a form of risk management primarily used to hedge against the risk of a contingent, uncertain loss. Insurance is defined as the equitable transfer of the risk of a loss, from one entity to another, in exchange for payment.
A pre-existing condition is a risk with extant causes that is not readily compensated by standard, affordable insurance premiums. Pre-existing condition exclusions by the insurance industry are meant to cope with adverse selection by potential customers. Only politicians would let you by "insurance" for a pre-existing condition.