THE RENAL HISTOPATHOLOGY OF ESSENTIAL MALIGNANT HYPERTENSION IN BLACK SOUTH AFRICANS

The renal histopathology of essential malignant phase hypertension in two groups of black South Africans was studied. The first, an autopsy series, consisted of material obtained in 1956-1961, a period when adequate antihypertensive therapy had not yet become generally available. The second group, a renal biopsy series, was from an era when effective antihypertensive therapy was available (1979-1989). The study showed that the clinical and histopathological changes of malignant hypertension were similar in both the pre-treatment and treatment eras. Fibrinoid necrosis was found in 92% of the autopsy sections and 44% of the biopsies. While mucinous, onion-skin and fibrotic changes of the blood vessels were commonly found, they were not invariably present and could not be considered the histopathological hallmark of malignant nephrosclerosis. It was often impossible on histological examination to distinguish malignant nephrosclerosis arising de novo from that superimposed on long-standing previous benign hypertension. Replication of internal elastic lamina, which has been considered a marker of long-standing previous benign hypertension, was a nonspecific finding and was frequently observed in young hypertensive subjects with a short clinical history. When fibrinoid necrosis is present, diagnosis of malignant nephrosclerosis can be made with confidence in black South Africans.