Background: Only minor changes of skin capillary morphology have been described in diabetic patients by means of capillaroscopy, whereas cutaneous microvascular dysfunction is well known. We examined correlations between functional and morphological abnormalities of the capillaries in Type 1 and 2 diabetic patients and the influence of diabetes duration on capillary morphology.
Patients and methods: Density, diameters and morphology of nailfold capillaries were investigated in diabetic patients, 16 Type 1 and 19 Type 2, and compared to age- and sex-matched control groups. Capillary blood cell velocities (CBV) during rest and after 3-minute arterial occlusion were measured in the dorsal middle phalangeal area of the left ring finger by means of laser Doppler anemometry.
Results: Capillary density, width and arterial limb diameter were similar in Type 1 and 2 diabetic patients compared to their controls. Capillary diameters of the apical part and the venous limb were enlarged in the combined analysis of Type 1 and 2 diabetic patients compared to the control group (apex: 19.2 +/- 0.6 microns vs 17.4 +/- 0.6 microns, p = 0.0243; venous limb: 17.3 +/- 0.5 microns vs 15.9 +/- 0.4 microns, p = 0.0238). Tortuous capillaries were more often observed in Type 1 (n = 13 vs n = 7, p = 0.028) and 2 diabetic patients (n = 16 vs n = 9, p = 0.019) than in controls. In Type 1 diabetic patients an inverse correlation (r = -0.52; p = 0.019) was found between capillary density and resting CBV. In Type 2 diabetic patients capillary apex diameter correlated positively with peak CBV (r = 0.49; p = 0.017). Disease duration correlated inversely with arterial limb diameter (r = -0.48; p = 0.020) and width of the capillaries (r = -0.48; p = 0.018) in Type 2 diabetic patients.
Conclusion: Tortuous and dilated capillaries, indicating microangiopathy, were found in the skin of diabetic patients by means of capillaroscopy. Using laser Doppler anemometry it is possible to assess impairment of postocclusive reactive hyperemia, due to diabetic microvascular dysfunction, in single capillaries. Correlations between morphological and functional microcirculatory alterations in diabetes may be explained by hemodynamic changes, depending on diabetes duration.