Skin Signs of Diabetes Bowel Disease and Occult Cancer
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Direct answer
Cutaneous markers of internal disease are skin signs that point to an underlying systemic problem, most often diabetes, insulin resistance, inflammatory bowel disease or an occult malignancy. Acanthosis nigricans usually signals insulin resistance, but sudden, widespread acanthosis in an adult raises suspicion of visceral adenocarcinoma. Pyoderma gangrenosum, necrolytic migratory erythema and the Leser-Trelat sign each point to a specific systemic process, and the examiner expects the candidate to name it.
What you must remember
- Acanthosis nigricans: Velvety, hyperpigmented thickening of the neck, axillae and groins, linked to insulin resistance, obesity and PCOS; sudden, extensive onset in an adult raises concern for malignancy.
- Pyoderma gangrenosum: A painful, rapidly enlarging ulcer with a violaceous, undermined edge, associated with inflammatory bowel disease, rheumatoid arthritis and haematological disorders, with pathergy as a characteristic feature.
- Necrolytic migratory erythema: Annular, blistering, erosive plaques on the groin, perineum and extremities, with glossitis and weight loss; a clue to glucagonoma.
- Leser-Trelat sign: Sudden eruption of many itchy seborrhoeic keratoses, classically in association with gastric adenocarcinoma.
- Dermatomyositis: Heliotrope rash and Gottron papules, with an association with occult malignancy in older adults.
- Dermatitis herpetiformis: Grouped itchy vesicles on extensor surfaces, linked to gluten sensitivity and IgA deposition in coeliac disease.
- Tripe palms: Diffuse hyperkeratotic thickening of the palms with accentuated creases, classically linked to internal malignancy.
A new rash in a 54-year-old with weight loss
A 54-year-old man has a few months of weight loss and epigastric discomfort, and over three weeks he has developed a crop of itchy, greasy, wart-like lesions across the trunk. Most seborrhoeic keratoses are benign and stable, so their sudden multiplicity is the clue.
- Treat the sign as the working diagnosis: In this setting the Leser-Trelat sign is the working diagnosis until proven otherwise.
- Scope the stomach: Upper gastrointestinal endoscopy with biopsy of any gastric lesion is indicated.
- Image the chest and abdomen: Cross-sectional imaging of the abdomen and chest follows.
- Run basic tests: Full blood count, liver function tests and stool occult blood help frame the search.
The skin lesions are not the diagnosis in themselves; they are the warning.
Contrast this with a 40-year-old woman who has long-standing acanthosis of the neck and axillae and a body mass index of 32. The picture fits insulin resistance, and the right action is metabolic screening with fasting glucose and HbA1c rather than a cancer hunt. Recognising sudden onset against long-standing change is the skill the examiner is testing.
Where the exam tries to catch you
Examiners test whether the candidate separates benign from alarming versions of each sign.
- Trap: treating all acanthosis as either benign or malignant. Correct: long-standing, symmetric acanthosis in an obese or insulin-resistant patient is benign, while sudden, florid or unexplained acanthosis, especially with weight loss, points to malignancy.
- Trap: diagnosing pyoderma gangrenosum without excluding infection and vasculitis. Correct: it is a diagnosis of exclusion, and surgical debridement at a pathergy site can make it worse.
- Trap: mistaking necrolytic migratory erythema for psoriasis or zinc deficiency. Correct: serum glucagon and zinc measurement separate them, and glucagonoma is linked with diabetes, anaemia and venous thrombosis.
- Trap: treating the Leser-Trelat sign as proof of cancer. Correct: it is a prompt for cancer screening, not proof of cancer.
Frequently asked questions
What does sudden acanthosis nigricans in an adult suggest?
Sudden, widespread acanthosis nigricans in an adult raises concern for an internal malignancy, classically gastric or other visceral adenocarcinoma, particularly when it arises without obesity or insulin resistance. Evaluation includes upper gastrointestinal endoscopy, cross-sectional imaging and biopsy of suspicious lesions.
Why is pyoderma gangrenosum a diagnosis of exclusion?
Pyoderma gangrenosum has no specific test, so infection, vasculitis and malignancy must be excluded before the diagnosis is accepted. Biopsy usually shows a nonspecific neutrophilic infiltrate, and the pathergy phenomenon, where new lesions form at sites of trauma, supports the diagnosis.
Which tumour causes necrolytic migratory erythema?
Glucagonoma, an alpha-cell tumour of the pancreas, causes necrolytic migratory erythema, typically with diabetes, weight loss, anaemia and glossitis. Serum glucagon measurement supports the diagnosis, and surgical resection or somatostatin analogues are the main management options.
What does the Leser-Trelat sign indicate?
Leser-Trelat sign is the sudden appearance of many itchy seborrhoeic keratoses, and it signals an underlying internal malignancy, most often gastric adenocarcinoma. It should prompt a search for occult cancer rather than reassurance that the lesions are benign.
Which skin condition is linked to coeliac disease?
Dermatitis herpetiformis is an itchy, grouped vesicular eruption on the extensor surfaces that is closely linked to coeliac disease through gluten-dependent IgA deposition. A gluten-free diet controls the rash, and coeliac screening is advised for every patient diagnosed with it.