Dermatology, Venereology and Leprosy
Skin Signs of Systemic Disease
Skin signs of systemic disease for MBBS and NEET-PG: acanthosis nigricans and diabetes, thyroid skin changes, erythema nodosum and pyoderma gangrenosum, mapped to NMC codes DR18.
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Skin Signs of Systemic Disease
Skin signs of systemic disease for MBBS and NEET-PG: acanthosis nigricans and diabetes, thyroid skin changes, erythema nodosum and pyoderma gangrenosum, mapped to NMC codes DR18.
The skin is a window on internal disease, and specific cutaneous signs point to systemic diagnoses. This chapter covers the cutaneous features of type 2 diabetes including acanthosis nigricans and necrobiosis lipoidica, the skin changes of hypothyroidism and hyperthyroidism, and reactive signs such as erythema nodosum and pyoderma gangrenosum.
High-yield: Skin Signs of Systemic Disease
- The skin often reflects internal disease, so a cutaneous sign can point to a systemic diagnosis such as diabetes or thyroid disorder.
- Acanthosis nigricans is velvety hyperpigmented thickening of the flexures and is a marker of insulin resistance and type 2 diabetes.
- Sudden extensive acanthosis nigricans in an adult can be a paraneoplastic sign, classically of gastric adenocarcinoma.
- Diabetic dermopathy produces brown atrophic shin patches, and necrobiosis lipoidica gives yellowish atrophic plaques with telangiectasia on the shins.
- People with diabetes are prone to recurrent skin infections, including candidiasis, boils and erythrasma.
- Poorly controlled diabetes predisposes to serious infections such as malignant otitis externa and mucormycosis.
- Hypothyroidism causes dry, coarse, cool skin with a non-pitting puffiness (myxoedema) and diffuse hair thinning with loss of the outer eyebrows.
- Hyperthyroidism causes warm, moist skin, and Graves' disease can produce pretibial myxoedema and thyroid acropachy.
- Vitiligo and alopecia areata are autoimmune conditions that cluster with autoimmune thyroid disease.
- Xanthomas, yellowish lipid deposits, signal hyperlipidaemia, and xanthelasma around the eyelids is the commonest form.
- Erythema nodosum, tender red shin nodules, is a reactive sign linked to streptococcal infection, sarcoidosis, tuberculosis, inflammatory bowel disease and drugs.
- Pyoderma gangrenosum, a rapidly enlarging painful ulcer with a violaceous undermined edge, is associated with inflammatory bowel disease and other systemic conditions.
- Generalised pruritus without a primary rash can indicate systemic disease such as cholestasis, chronic kidney disease, lymphoma or thyroid disorder.
- Recognising these cutaneous markers allows earlier diagnosis and treatment of the underlying systemic illness.
Skin markers of systemic disease
- **Diabetes:** Acanthosis nigricans, necrobiosis lipoidica, recurrent infections.
- **Hypothyroidism:** Dry coarse cool skin, myxoedema, loss of outer eyebrows.
- **Hyperthyroidism:** Warm moist skin; Graves' pretibial myxoedema and acropachy.
- **Reactive signs:** Erythema nodosum, pyoderma gangrenosum, xanthomas, generalised pruritus.
NMC competencies in this chapter
- **DR18.1:** Cutaneous features of type 2 diabetes
- **DR18.2:** Cutaneous features of hypothyroidism and hyperthyroidism
Frequently Asked Questions
What is acanthosis nigricans a sign of?
Velvety hyperpigmented thickening of the flexures that marks insulin resistance and type 2 diabetes. A sudden extensive form in an adult can be paraneoplastic, classically with gastric adenocarcinoma.
What skin changes suggest hypothyroidism?
Dry, coarse, cool skin with a non-pitting puffiness called myxoedema, diffuse hair thinning and loss of the outer third of the eyebrows.
What conditions cause erythema nodosum?
Tender red nodules on the shins linked to streptococcal infection, sarcoidosis, tuberculosis, inflammatory bowel disease and certain drugs, making it a useful reactive marker.
When does generalised itching suggest systemic disease?
Persistent itching without a primary rash can point to cholestasis, chronic kidney disease, lymphoma or thyroid disorder, so a systemic cause should be sought.
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