Incidence and significance of muscle capillary basal lamina thickness in juvenile diabetes.

The mean minimal and average basal lamina thickness (MBLT and ABLT) of 17 to 20 muscle capillaries were measured in 26 overt juvenile diabetics and in 26 nondiabetic patients of similar age. The mean MBLT was significantly increased in diabetics although 17 of the individual values in diabetics overlapped those obtained in nondiabetics. Segmental and focal fluctuations in basement membrane width appeared to be the most important cause of variance, particularly in thick walled vessels, although multiple instrumental and technical sources of error were also present. As a result, in diabetics there was a mean variability of +/-25% when measurements from two different sets of capillaries in the same subject were compared. Patients older than 12 years and diabetics with longer duration of the disease or abnormal findings on ophthalmoscopic examination exhibited a significant increase in capillary basal lamina. The mean ABLT averaged 1.8 times the mean MBLT, but the relative individual measurements as well as statistical correlations with clinical parameters were similar. Muscle capillary basement membrane hypertrophy, as quantitated by the present methods, does not seem to be an early, sensitive or consistent finding to identify individual diabetics.