Cutaneous Manifestations of Diabetes Mellitus
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Direct answer
Cutaneous manifestations of diabetes mellitus include specific lesions such as necrobiosis lipoidica and diabetic dermopathy, markers of insulin resistance such as acanthosis nigricans, and a raised risk of bacterial and fungal infection. Necrobiosis lipoidica is a shiny, atrophic plaque on the shins that can ulcerate, whereas diabetic dermopathy is a harmless brown macule. Recognising them separates benign findings from those needing treatment or a systemic search.
What you must remember
- Necrobiosis lipoidica: shiny, yellow-brown, atrophic plaques with telangiectasia on the pretibial skin, which can ulcerate and are treated with potent topical or intralesional steroids.
- Diabetic dermopathy: well-defined brown atrophic macules on the shins, often called shin spots, which are asymptomatic and need reassurance only.
- Acanthosis nigricans: velvety hyperpigmented thickening of the neck, axillae and groin, marking insulin resistance and hyperinsulinaemia.
- Bullosis diabeticorum: tense, non-inflammatory blisters on the feet, legs and hands that heal without scarring over a few weeks.
- Scleredema diabeticorum: thickened, indurated skin over the upper back and neck, associated with long-standing diabetes.
- Stiff hand syndrome: limited mobility of the finger joints from glycation of collagen, also called cheiroarthropathy.
- Infections: candidal intertrigo, dermatophytosis, staphylococcal folliculitis and furunculosis, and mucormycosis in uncontrolled hyperglycaemia or ketoacidosis.
A diagnostic approach to diabetic skin lesions
Skin lesions in diabetes are often recognised by site and morphology before any test is ordered. The sequence below helps separate benign findings from infections and systemic markers.
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Start with site and morphology. Atrophic lesions on the shins suggest necrobiosis lipoidica or dermopathy, while velvety thickening of the neck and flexures points to acanthosis nigricans.
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Separate benign from ulcerating lesions. Diabetic dermopathy needs only reassurance, whereas necrobiosis lipoidica can break down and needs specialist review.
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Look for infection first when lesions are red or itchy. Candidal intertrigo and tinea are common, and skin breakdown can lead to deeper bacterial infection that needs culture-guided antibiotics.
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Check for a systemic cause. Acanthosis nigricans with sudden onset or rapid spread in an adult should prompt a search for malignancy, with gastric adenocarcinoma the classic association.
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Assess metabolic control. Eruptive xanthomas signal severe hypertriglyceridaemia and need lipid-lowering treatment alongside glycaemic control.
Where the exam tries to catch you
Skin questions in diabetes usually test lesion identification, the benign-versus-serious distinction, or the systemic link.
- Trap: calling necrobiosis lipoidica and diabetic dermopathy the same condition. Correct: dermopathy is a harmless set of shin spots, while necrobiosis lipoidica is an atrophic plaque that can ulcerate and needs specialist treatment.
- Trap: treating acanthosis nigricans as a purely cosmetic skin problem. Correct: it marks insulin resistance, so hyperinsulinaemia and, when sudden in adults, a possible malignancy need evaluation.
- Trap: assuming diabetic blisters are infected. Correct: bullosis diabeticorum forms tense, sterile blisters on the feet and legs that heal without scarring.
Frequently asked questions
What is the difference between necrobiosis lipoidica and diabetic dermopathy?
Necrobiosis lipoidica is a shiny, atrophic, yellow-brown plaque with telangiectasia on the shins that can ulcerate. Diabetic dermopathy is a set of harmless, well-defined brown macules on the shins that needs no treatment. The distinction matters because necrobiosis lipoidica may need topical or intralesional steroids.
Why does acanthosis nigricans in an adult raise concern for malignancy?
Acanthosis nigricans reflects insulin resistance and hyperinsulinaemia, but a sudden or rapidly spreading onset in an adult raises concern for an underlying malignancy. Gastric adenocarcinoma is the classic association. The skin finding should therefore prompt a search for an occult cancer.
Which skin infections are most common in diabetes mellitus?
Candidal infections, dermatophyte infections and bacterial infections such as staphylococcal folliculitis are common in diabetes. Diabetic foot infections become a major concern when the skin breaks down. Mucormycosis is a dangerous infection in uncontrolled hyperglycaemia or ketoacidosis and needs urgent treatment.
How is bullosis diabeticorum distinguished from an infected bullous lesion?
Bullosis diabeticorum produces tense, non-inflammatory blisters on the feet, legs and hands that are sterile and heal without scarring over a few weeks. Infected bullous lesions are usually inflamed and need culture and antibiotic treatment. The absence of inflammation and the spontaneous healing are the key clues.