Dermatological manifestations of diabetes mellitus

Overview

Key dermatological manifestations of diabetes
ConditionKey featuresMechanism/association
Acanthosis nigricansVelvety, hyperpigmented, thickened skin at flexures (back of neck, axillae, groin); asymptomatic, does not itch or wash offInsulin resistance → hyperinsulinaemia → IGF-1 receptor activation → keratinocyte and fibroblast proliferation
Necrobiosis lipoidica diabeticorumRed-brown papules on shins → waxy yellow-brown plaques, violaceous border, central atrophy with telangiectasia; ulcerate in ~35%Microangiopathy; can occur with well-controlled glucose and may precede diabetes diagnosis
Lichen sclerosusWhite atrophic plaques on vulva/perianal skin; causes itch and soreness; ~5% risk of squamous cell carcinomaAutoimmune; associated with type 1 diabetes (shared HLA haplotypes)
Diabetic dermopathySmall bilateral dull red papules on shins healing to depressed, hyperpigmented scars ('shin spots'); most common skin finding in diabetesMicroangiopathy and minor trauma
Fungal/candidal infectionsCandida intertrigo, vulvovaginal candidiasis, onychomycosis - all significantly more common in diabetesHyperglycaemia provides fungal substrate; impaired immune clearance

Condition	Key features	Mechanism/association
Acanthosis nigricans	Velvety, hyperpigmented, thickened skin at flexures (back of neck, axillae, groin); asymptomatic, does not itch or wash off	Insulin resistance → hyperinsulinaemia → IGF-1 receptor activation → keratinocyte and fibroblast proliferation
Necrobiosis lipoidica diabeticorum	Red-brown papules on shins → waxy yellow-brown plaques, violaceous border, central atrophy with telangiectasia; ulcerate in ~35%	Microangiopathy; can occur with well-controlled glucose and may precede diabetes diagnosis
Lichen sclerosus	White atrophic plaques on vulva/perianal skin; causes itch and soreness; ~5% risk of squamous cell carcinoma	Autoimmune; associated with type 1 diabetes (shared HLA haplotypes)
Diabetic dermopathy	Small bilateral dull red papules on shins healing to depressed, hyperpigmented scars ('shin spots'); most common skin finding in diabetes	Microangiopathy and minor trauma
Fungal/candidal infections	Candida intertrigo, vulvovaginal candidiasis, onychomycosis - all significantly more common in diabetes	Hyperglycaemia provides fungal substrate; impaired immune clearance

🚨
Acanthosis nigricans is linked to insulin resistance, not hyperglycaemia per se - more strongly associated with type 2 diabetes, obesity, and PCOS than type 1. Sudden onset in a non-obese adult with weight loss is a red flag for paraneoplastic acanthosis nigricans (especially gastric adenocarcinoma).

Investigations

🥇 First-line

•fasting blood glucose and HbA1c - screen for or monitor diabetes in any patient with acanthosis nigricans, NLD, or recurrent candidal infections

•clinical diagnosis for acanthosis nigricans, diabetic dermopathy, and NLD - based on appearance and clinical context

🏆 Gold standard

•skin biopsy - for lichen sclerosus (confirm diagnosis and exclude malignancy) and any lesion suspicious for malignancy

Differential diagnosis

•Lichen sclerosus vs vitiligo - vitiligo causes depigmentation but skin texture is normal; no atrophy, no itch, no plaque

•Lichen sclerosus vs vulvovaginal candidiasis - candidiasis causes itch/soreness with erythema, satellite lesions, and white discharge, not white atrophic plaques

•Lichen sclerosus vs vulval SCC - SCC more likely with raised, indurated, or ulcerated lesions; biopsy required to exclude malignancy

Management

•Acanthosis nigricans - First-line: optimise glycaemic control and weight management; skin changes often partially reversible with treatment of insulin resistance

•Necrobiosis lipoidica - First-line: potent topical corticosteroids (e.g. clobetasol propionate) or intralesional triamcinolone for active non-ulcerated lesions; glycaemic optimisation does not reliably improve NLD

•Lichen sclerosus - First-line: clobetasol propionate 0.05% ointment - BASHH 3-month reducing regimen: once daily 4 weeks → alternate days 4 weeks → twice weekly 4 weeks; long-term maintenance required; annual review for malignant change

•Fungal/candidal infections - First-line: topical antifungal (clotrimazole or miconazole); Second-line: oral fluconazole or terbinafine for recurrent, extensive, or nail infections; optimise glycaemic control to reduce recurrence

⚠️
Lichen sclerosus requires long-term follow-up even when well controlled - approximately 5% lifetime risk of vulval squamous cell carcinoma. Patients should report new ulceration, induration, or rapidly changing lesions.