Lower melanin content in the skin of type 1 diabetic patients and the risk of microangiopathy.

Various skin diseases are commonly observed in diabetic patients. Typical biophysical properties of diabetic skin such as lower skin elasticity, decreased water content in stratum corneum, increased itching and sweating disturbances are reported. The aim of the study was to examine the distribution and intensity of skin pigmentation in diabetic patients in correlation with the metabolic control and with presence of microangiopathy. The study was conducted on 105 patients (42 men and 63 women, median age 31), with type 1 diabetes (DM1). The control group of 53 healthy individuals (22 men and 31 women) was age- and sex-matched. Skin pigmentation was measured at 3 different locations of the body (cheek, dorsal surface of a forearm and dorsal surface of a foot) using Mexameter® MX 18. We calculated melanin index (MI) by the meter from the intensities of absorbed and reflected light at 880 nm. Patients with DM1 had lower MI on the foot (173.2 ± 38.8 vs. 193.4 ± 52.7, p=0.016) as compared to controls. In the univariate analysis cheek MI was negatively related to HbA1c level (β=-4.53, p=0.01). Forearm MI was negatively associated with daily insulin dose (β=-0.58, p=0.01), BMI (β=-3.02, p<0.001), waist circumference (β=-0.75, p=0.009), serum TG concentration (β=-18.47, p<0.001) and positively with HDL cholesterol level (β=15.76, p=0.02). Diabetic patients with hypertension had lower foot MI values (β=-18.28, p=0.03). Lower MI was associated with the presence of diabetic neuropathy (β=-18.67, p=0.04) and retinopathy (β=-17.47, p=0.03). In conclusion, there seems to be loss of melanocytes in type 1 diabetes. The melanin content is related to glycemic control of diabetes and obesity. The lower melanin content the higher possibility of microangiopathy. This is a first report in the literature devoted to distribution of melanin in the skin of type 1 diabetic patients.