Learning Objective
Recognize major systemic diseases that present with characteristic skin changes, understand their underlying mechanisms, and identify when skin findings may indicate an underlying systemic or malignant condition.
Clinical Principles
- Skin lesions can be the initial sign of an underlying systemic disorder.
- Treating the primary systemic disease often leads to improvement or resolution of the dermatologic manifestations.
- Some skin changes may also serve as paraneoplastic markers.
Activity
Acanthosis Nigricans
Clinical Features:
- Raised, thickened, hyperpigmented skin
- Common sites: axillae, groin, posterior neck
Histopathology:
- Elevated dermal papillae
- Hyperkeratosis
- Increased melanin in the basal layer
Associated With:
- Obesity
- Hyperinsulinism (insulin resistance, diabetes)
- Paraneoplastic form: associated with cancers, especially gastrointestinal malignancies
Clinical Importance:
- Sudden onset in adults → consider occult malignancy
Systemic Lupus Erythematosus (SLE)
Typical Presentation:
- Rash, joint pain, fever
Cutaneous Finding:
- Malar rash:
- Bilateral
- Erythematous
- Involves cheeks
- Crosses the bridge of the nose
- May occur with other photosensitive rashes (as reviewed in cutaneous lupus).
