Focal or multifocal, circular to irregularly shaped lesion that are raised above the normal surface of the colony. They consist of coenosteal skeleton that develops between and over normal calices. The affected area generally has a reduction or complete loss of polyps. There is generally a thin layer of intact tissue that is much lighter than the surrounding area, and often becomes completely white due to absence of zooxanthellae. The “Bubbling” of tissue may occur at margin of lesion. These can be 10-cm or more in diameter. They develop on any region of the colony, and often proliferate over time, expanding in size and number. Lesions often coalesce over time. In larger lesions, the central, oldest part of the GA may die.