An 80-year-old woman presents with severe, persistent itching that has progressively worsened over the past 6 years. The itch is generalized but most pronounced on her arms and legs, often disrupting her sleep. She reports scratching to the point of bleeding and has had multiple episodes of secondary cellulitis requiring antibiotics. Her medical history includes type 2 diabetes, hypertension, asthma, and seasonal allergies. She recalls that several family members, including two grandchildren, have eczema and allergic rhinitis. She denies new medications, topical products, or changes in her environment.

On physical examination, there are crusted excoriations distributed symmetrically over the proximal and distal upper and lower extremities, with background xerosis. No primary vesicles, burrows, or nodules are seen. There is no lymphadenopathy. Routine labs, including CBC, renal, hepatic, and thyroid function tests, are within normal limits.