Skin tag as a cutaneous marker for impaired carbohydrate metabolism: a case-control study.
Skin tags are common benign skin tumors usually occurring on the neck and major flexors of older people. A possible association with impaired carbohydrate metabolism has been suggested in previous studies, but the results are not conclusive. To investigate and compare the prevalence of diabetes and impaired glucose tolerance (IGT) in patients with skin tag and a control group. A case-control study was conducted in individuals over 15 years old, comparing cases (n = 104) with at least three skin tags and age-, sex-, and body mass index (BMI)-matched controls (n = 94) without skin tag. Cases and controls were recruited from patients consecutively seen at an academic outpatient dermatology clinic. All patients underwent a standard 2-h oral glucose tolerance test with 75 g glucose. Patients with skin tag had higher frequency of diabetes than the control group (23.07% vs. 8.51%, chi(2)-test, P = 0.005). The difference in the frequency of IGT was not significant (13.46% vs. 10.63%, chi(2)-test, P = 0.543). There was a positive correlation between the total number of skin tags and the mean fasting plasma glucose (Pearson correlation, r = 0.260, P = 0.031); patients with more than 30 skin tags were particularly at an increased risk of diabetes (52.0%). No correlation was found between the number of skin tags and BMI. We did not find any correlation between the anatomical localization of skin tags and impaired carbohydrate metabolism, except for skin tags under the breast in women. These results show an increased risk of diabetes mellitus in patients with multiple skin tags. With regard to the importance of early diagnosis of diabetes, we recommend a high level of suspicion for impaired carbohydrate metabolism in patients with skin tag.