Special circumstances exist to protect an unregistered purchaser of immovable property against execution by a judgment creditor where: (1) the purchaser and seller demonstrated clear intention to effect transfer; (2) the purchaser did all that was required to receive transfer (paid purchase price, paid transfer fees, completed requisite processes); (3) the impediment to registration was not of the purchaser's making but was attributable to a third party beyond the purchaser's control; and (4) the purchaser was an innocent purchaser who acquired the property when it was free from any right of preference. In such circumstances, although the judgment debtor retains registered title, this is 'title on paper only' where the debtor has relinquished all rights in the property, and it would be unjust to allow execution to proceed. Personal rights acquired through an agreement of sale by an innocent purchaser are not inferior to personal rights acquired through registration of a caveat by a subsequent judgment creditor. Courts will protect the equitable interest of such purchasers to prevent the judgment debtor from benefiting twice from the same property and to avoid imposing double loss on an innocent purchaser.