Evidence for two populations of fatty streaks with different roles in the atherogenic process.

Isoenzymes of glucose-6-phosphate dehydrogenase, used as cellular markers, showed that a minority of fatty streaks have clonal characteristics intermediate between those of normal arterial wall and those of fibrous plaques, suggesting that such streaks are evolving into fibrous plaques. "Intermediate" fatty streaks are found to cluster in patients in the middle-age years, suggesting that few fatty streaks evolve into plaques in the advanced years. It is suggested that two populations of fatty streaks exist: one destined, perhaps by its location or risk factors, to develop into fibrous plaques; and a second which remains as fatty streaks and never goes on to become fibrous plaques. This hypothesis helps to explain some of the evidence disclaiming the fatty streak as a forerunner of the atherosclerotic plaque.