DermatologyTier 2Disease (DEADMAN)

Cutaneous manifestations of systemic disease - diabetes-related skin

Description

Diabetes mellitus produces a range of characteristic skin manifestations - necrobiosis lipoidica, diabetic dermopathy, acanthosis nigricans, and increased infection susceptibility among the more recognised - reflecting the combined effects of microvascular disease, glycation, and altered immune function

Skin manifestations are common in diabetes and can occasionally be the presenting clue prompting diabetes screening, particularly acanthosis nigricans in the context of insulin resistance

Necrobiosis lipoidica - a granulomatous, microvascular-related process causing atrophic, yellow-brown plaques with telangiectasia, classically pretibial; diabetic dermopathy ("shin spots") - small, atrophic, hyperpigmented macules, thought to relate to microvascular disease, very common and often under-recognised; acanthosis nigricans - velvety hyperpigmentation in flexural areas (neck, axillae), reflecting insulin resistance and hyperinsulinaemia's proliferative effect on keratinocytes/fibroblasts rather than diabetes itself
Increased susceptibility to skin infection (bacterial and fungal, particularly candidiasis) reflects the combination of hyperglycaemia providing a favourable growth substrate and impaired neutrophil/immune function

Largely clinical diagnosis based on characteristic appearance and distribution; necrobiosis lipoidica may require biopsy if the diagnosis is uncertain, given its granulomatous histological pattern
Acanthosis nigricans in a non-obese patient, or with rapid onset/atypical distribution, should prompt consideration of an underlying malignancy (paraneoplastic acanthosis nigricans, classically gastric adenocarcinoma) rather than assuming insulin resistance as the only cause

Optimising glycaemic control is the primary management approach across these manifestations, though established necrobiosis lipoidica lesions often persist despite good glycaemic control; topical/intralesional corticosteroids can help necrobiosis lipoidica symptomatically
Treat skin/fungal infections promptly given the increased susceptibility, and consider improving glycaemic control as part of infection management, not just antimicrobial treatment alone

Insulin resistance/metabolic syndrome (acanthosis nigricans), paraneoplastic acanthosis nigricans (malignancy association when atypical), candidal skin/mucosal infection, diabetic foot disease

Acanthosis nigricans is a marker of insulin resistance/hyperinsulinaemia rather than diabetes itself - it can occur in obesity/PCOS without frank diabetes, and atypical or rapidly progressive presentations should prompt malignancy screening rather than being assumed to reflect simple insulin resistance

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