The Capillary Vascular Lesion in Diabetes Mellitus: Its Clinical Manifestations and Significance
Authors: Letter Louis 
Published: December 2014

The clinical syndrome associated with the capillary vascular lesion in diabetes stems from two primary sites: the eyes and the kidneys. In each of these locations th vascular lesion is quite specific for diabetes and the clinical consequences are very serious. There is evidence suggesting a common morphologic and biochemical basis for the microaneurysms in the retina and the hyaline deposits in the glomeruli. There is no explanation for the apparent limitation of this process to these two capillary regions in the diabetic human or animal. Clinically, manifestations of lesions in either the retina or the kidneys—usually simultaneously in the two organs—are found in both young and old diabetics. Although these were originally described in the older age group, and with the implication of milder diabetes as the background, careful study of young diabetics with long survival after the onset of diabetes has emphasized the high incidence of the capillary vascular lesion and its dominant role in the morbidity and mortality of the victims.
Nearly twenty years have elapsed since the description by Kimmelsteil and Wilson of a clinical syndrome in diabetics with intercapillary glomerulosclerosis. To this renal vascular lesion has since been added the retinal capillary microaneurysm as the specific morphologic expression of prolonged diabetes, not only in man but presumably also in the experimental diabetic animal. The present discussion is limited to the clinical aspects of the renal lesion.
The clinical statistics of the renal vascular lesion in diabetes are well known. While numerically the clinical syndrome is highest after the fifth decade, this is simply because the diabetic population increases rapidly at this period. Percentage-wise and mortality-wise, the syndrome is most prevalent in the third to fifth decades, comprising the patients with onset of diabetes between the first and third decades. Whether one examines the very large autopsy series reported by Bell or the clinical statistics analyzed by Keiding et al., the predominance of the renal lesion as the major cause of morbidity and mortality in diabetics under age fifty is overwhelming. In the autopsy series of diabetics with glomerulosclerosis who were under age fifty at death, 46 per cent had the nephrotic syndrome and 63 per cent had uremia, in addition to a high incidence of hypertension and of renal arteriosclerosis. In the subjects with a duration of diabetes of fifteen to twenty years and onset before age forty, 75 per cent of the deaths were from vascular, chiefly renal, disease. It is interesting that the other 25 per cent had only minimal vascular lesions—exactly the same percentage with “minimal complications” was found in Keiding's clinical series among the group with “poor control” of diabetes. The incidence of “nephropathy” in Keiding's series of 451 diabetics with onset of diabetes before age thirty and duration of more than ten to fifteen years was 22 per cent, all occurring in the inadequately controlled group. In spite of the frequency of hypertension in the diabetic with capillary vascular lesions, malignant hypertension was very rare—Bell did not find a single instance among 119 cases of uremia in diabetic glomerulosclerosis.