Describes symmetrical, brown, velvety plaques that are often found on the neck, axilla and groin.

Causes

• type 2 diabetes mellitus
• Most common associated malignancy: gastrointestinal cancer
• obesity
• polycystic ovarian syndrome
• acromegaly
• Cushing's disease
• hypothyroidism
• familial
• Prader-Willi syndrome
• drugs
  • combined oral contraceptive pill
  • nicotinic acid

Pathophysiology

• insulin resistance → hyperinsulinemia → stimulation of keratinocytes and dermal fibroblast proliferation via interaction with insulin-like growth factor receptor-1 (IGFR1)