Diabetes mellitus (DM) is a worldwide problem and the most common endocrine disorder. Its prevalence is increasing in the present scenario of a sedentary lifestyle in the general population [1]. Abnormalities of insulin and elevated blood glucose levels lead to metabolic, vascular, neurological, and immunological abnormalities [2]. Affected organs include the cardiovascular, renal, and nervous systems, as well as the eyes and skin. The skin is affected by both acute metabolic derangements and chronic degenerative complications of diabetes [3]. Although the mechanism for many diabetes-associated skin conditions remains unknown, the pathogenesis of others is linked to abnormal carbohydrate metabolism, altered metabolic pathways, atherosclerosis, microangiopathy, neuronal degeneration, and impaired host mechanisms [4]. The association of certain skin diseases with diabetes mellitus has been well recognized, with an incidence ranging from 11.4% to 71% [5]. Diabetes mellitus comprises a heterogeneous group of disorders characterized by variable degrees of insulin resistance, impaired insulin secretion, and increased glucose production, preceded by a period of abnormal glucose homeostasis classified as impaired fasting glucose or impaired glucose tolerance [6]. Numerous skin lesions are associated with either type 1 or type 2 diabetes mellitus, specific chronic complications of the disease, the use of antibiotic drugs, and certain endocrine and metabolic disorders that cause secondary diabetes mellitus. Various cutaneous manifestations are significantly associated with diabetes compared with control groups [7]. There is no strict classification of skin lesions related to diabetes mellitus; therefore, grouping them under broad headings provides an overview of the various types of skin lesions occurring in diabetes [8].

This cross-sectional study was conducted in the Department of Medicine, Government Headquarters Hospital, Kallakurichi, Tamil Nadu, from June 2019 to March 2020 (10 months). A total of 300 patients with diabetes mellitus attending the diabetic clinic and medical outpatient department were included. Inclusion criteria Patients with diabetes mellitus attending the diabetic clinic and medical outpatient department during the study period. Exclusion criteria Patients aged less than 12 years. A total of 300 patients with diabetes mellitus attending the diabetic clinic and medical outpatient department were evaluated. A detailed history was obtained and a clinical examination, with particular attention to the presence of cutaneous lesions, was performed. Fundus examination and routine blood and urine investigations were performed. Blood glucose values were expressed in mg/dL. Skin scrapings, direct potassium hydroxide examination, and fungal culture on Sabouraud agar were performed when indicated. Gram staining and culture of pus were carried out in selected cases to identify bacterial organisms. Histopathological examination of skin sections was performed wherever necessary to confirm the diagnosis. Statistical Analysis Data were analyzed using Statistical Package for the Social Sciences (SPSS), version 21. Continuous variables were summarized using mean and standard deviation, and categorical variables using frequencies and percentages. Associations between categorical variables were assessed using the chi-square test or Fisher’s exact test, as appropriate. Odds ratios were used to describe the strength of association. Statistical significance was set at p < 0.05. For categorical analyses of glycemic status, fasting and postprandial blood glucose were dichotomized at the median values observed in the study (176 mg/dL and 269 mg/dL, respectively).

A total of 300 patients with diabetes mellitus were analyzed; 149 were male (49.7%) and 151 were female (50.3%). Of these, 112 patients had cutaneous manifestations, giving a prevalence of 37.3%. Type 1 diabetes mellitus was present in 16 patients (5.3%), type 2 diabetes mellitus in 244 (81.3%), and 40 patients (13.3%) were unclassified. Among the 112 patients with cutaneous lesions, coronary artery disease was present in 20 (17.9%), metabolic syndrome in 20 (17.9%), diabetic retinopathy in 24 (21.4%), diabetic nephropathy in 15 (13.4%), peripheral vascular disease in 15 (13.4%), and diabetic neuropathy in 27 (24.1%). Blood glucose was analyzed as a risk factor for diabetic complications. A fasting blood glucose level >176 mg/dL was significantly associated with coronary artery disease (p = 0.001), metabolic syndrome (p = 0.015), diabetic retinopathy (p < 0.001), diabetic nephropathy (p = 0.003), peripheral vascular disease (p = 0.045), and diabetic neuropathy (p = 0.017). Similarly, a postprandial blood glucose level >269 mg/dL was significantly associated with all the above complications. Postprandial blood glucose showed stronger statistical associations with several complications. The common cutaneous presentations were further analyzed for associated risk factors. Age >50 years was significantly associated with pruritus (p = 0.025) and diabetic foot (p = 0.046). Table 1. Distribution of blood sugar values and age Fasting blood glucose (mg/dL) Postprandial blood glucose (mg/dL) Age Minimum 128 167 19 Maximum 388 506 71 Mean 182.91 286.33 49.7 Median 176 269 49.5 Standard deviation 47.187 66.134 13.19 Table 2. Diabetes mellitus complications Complication Frequency Percentage CAD 20 17.9 Metabolic syndrome 20 17.9 Diabetic retinopathy 24 21.4 Diabetic nephropathy 15 13.4 PVD 15 13.4 Diabetic neuropathy 27 24.1 Table 3. Risk factors for diabetes mellitus complications Present Absent Odds ratio Chi-square p-value CAD 17.0 40 7.367 11.333 0.001 Metabolic syndrome 15 42 3.571 5.666 0.015 Diabetic retinopathy 22 35 16.657 20.139 0.0001 Diabetic nephropathy 13 44 7.83 8.869 0.003 PVD 11 46 3.049 3.89 0.045 Diabetic neuropathy 19 38 2.938 5.4 0.017 A fasting blood glucose level >176 mg/dL was significantly associated with all the listed diabetic complications. Table 4. Postprandial blood sugar >269 and complications Present Absent Odds ratio Chi-square p-value CAD 18 39 12.231 14.899 0.0001 Metabolic syndrome 18 39 12.231 14.899 0.0001 Diabetic retinopathy 22 35 16.657 20.319 0.0001 Diabetic nephropathy 14 43 17.581 12.482 0.0001 PVD 12 45 4.662 5.871 0.014 Diabetic neuropathy 22 35 6.286 13.319 0.0001 A postprandial blood glucose level >269 mg/dL was significantly associated with all the listed diabetic complications. Table 5. Pattern of skin lesions Skin diseases Frequency Percentage Pruritus 14 12.5 Diabetic dermopathy 3 2.7 Necrobiosis lipoidica diabeticorum 2 1.8 Granuloma annulare 1 0.9 Diabetic bullae 3 2.7 Scleroderma-like syndrome 4 3.6 Diabetic foot 14 12.5 Fungal infection 19 17.0 Bacterial infection 14 12.5 Xanthoma 2 1.8 Insulin lipodystrophy 3 2.7 Nail changes 6 5.4 Perforating dermatosis 7 6.3 Vitiligo 3 2.7 Lichen planus 4 3.6 Bullous pemphigoid 1 0.9 Dermatitis herpetiformis 2 1.8 Psoriasis 3 2.7 Eczema 7 6.3 Total 112 100 Table 6. Risk-factor analysis for skin lesions in diabetes mellitus Present Absent Odds ratio Chi-square p-value Pruritus 3 52 0.241 4.905 0.025 Diabetic foot 10 45 2.944 3.89 0.046 Bacterial infection 5 50 0.533 1.148 0.217 Fungal infection 7 48 0.547 1.377 0.179 Dermatosis 3 50 0.764 0.117 0.521 Table 7. Type of diabetes mellitus and skin lesions Skin lesion Type of DM Present Absent Odds ratio Chi-square p-value Pruritus TYPE I 0 3 1.147 0.44 0.667 TYPE II 14 95 Diabetic foot TYPE I 0 3 0.44 0.667 TYPE II 14 95 Bacterial infection TYPE I 1 2 3.692 1.223 0.373 TYPE II 13 96 Fungal infection TYPE I 1 2 2.528 0.586 0.431 TYPE II 18 91 Perforating dermatosis TYPE I 1 2 8.583 3.859 0.178 TYPE II 6 103

In this study, 112 of 300 patients with diabetes mellitus had cutaneous lesions, giving a prevalence of 37.3%. The frequency of cutaneous manifestations reported in previous studies varies considerably because of differences in study populations, duration of diabetes, glycemic control, and methods of dermatological assessment [9]. Higher fasting and postprandial blood glucose categories were significantly associated with several diabetic complications. The cut-offs of >176 mg/dL for fasting glucose and >269 mg/dL for postprandial glucose corresponded to the median values observed in this study. As this was a cross-sectional study, these associations should be interpreted as associations rather than causal relationships [10,11]. Fungal infection was the most common cutaneous manifestation (17.0%), followed by pruritus, diabetic foot, and bacterial infection (12.5% each), and perforating dermatosis (6.3%). Age >50 years was significantly associated with pruritus (p = 0.025) and diabetic foot (p = 0.046). Sex was not significantly associated with the common skin lesions [12,13]. The type of diabetes was not significantly associated with the common skin lesions analyzed (p > 0.05). This comparison was limited by the small number of patients with type 1 diabetes and cutaneous lesions. Higher fasting and postprandial blood glucose categories were also significantly associated with diabetic foot in the present study. Fungal infection was significantly associated with coronary artery disease (p = 0.016), metabolic syndrome (p = 0.016), diabetic retinopathy (p = 0.006), and diabetic nephropathy (p = 0.04). Diabetic foot was significantly associated with diabetic retinopathy (p = 0.011), and pruritus was significantly associated with diabetic neuropathy (p = 0.016). The association between fungal infection and peripheral vascular disease was not statistically significant (p = 0.48). Limitations This was a single-center cross-sectional study; therefore, temporal and causal relationships cannot be established. The small number of patients with type 1 diabetes and cutaneous manifestations limits comparisons according to diabetes type. HbA1c was not reported, and glycemic status was assessed using fasting and postprandial blood glucose values

Cutaneous manifestations were identified in 37.3% of the 300 patients with diabetes mellitus. Fungal infection was the most common manifestation, followed by pruritus, diabetic foot, and bacterial infection. Older age was associated with pruritus and diabetic foot. Fungal infection was associated with coronary artery disease, metabolic syndrome, diabetic retinopathy, and diabetic nephropathy; diabetic foot was associated with diabetic retinopathy; and pruritus was associated with diabetic neuropathy. Routine skin examination may therefore provide useful clinical information in patients with diabetes mellitus

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