What is the cause and treatment for an adult or child with no significant medical history presenting with patches of bumpy skin resembling goose bumps and itching?

Keratosis Pilaris (Most Likely Diagnosis)

The most likely diagnosis is keratosis pilaris, a benign condition causing rough, bumpy skin resembling "goose bumps" with associated itching, treated primarily with liberal emollient use and mild topical corticosteroids if inflamed.

Clinical Presentation

Keratosis pilaris presents as small, rough bumps that feel like sandpaper or permanent goose bumps, typically affecting the outer upper arms, thighs, cheeks, and buttocks. The bumps are caused by keratin plugs blocking hair follicles, creating a characteristic follicular pattern. While not explicitly detailed in the provided guidelines, this presentation differs from the flexural distribution typical of atopic eczema 1.

Key Differential Diagnoses to Consider

Atopic Eczema

• Requires an itchy skin condition plus three or more criteria: history of itchiness in skin creases, history of asthma/hay fever or family history of atopic disease, general dry skin in past year, visible flexural eczema, and onset in first two years of life 1
• In children under 4 years, characteristically affects cheeks or forehead rather than flexural areas 2
• General dry skin (xerosis) progresses to inflammatory conditions with fissures 3

Secondary Bacterial Infection

• Look for crusting, weeping, or honey-colored discharge suggesting impetiginization 1, 3
• Send swabs for bacterial culture if suspected and treat with flucloxacillin 3

Scabies (Critical to Exclude)

• Intense itch worse at night, affecting all body regions except the head, appearing out of proportion to physical findings 4
• Look for burrows (pathognomonic sign), typically up to 1 cm in length, especially in finger webs 1, 4
• Close contacts also itching is highly suggestive 4

Initial Management Approach

First-Line Treatment

• Apply emollients liberally and frequently (at least twice daily and as needed throughout the day) to lock in moisture when skin is most hydrated 2, 3
• Use moisturizers with high lipid content, particularly in elderly patients 1, 2
• Avoid hot showers and excessive soap use, which remove natural lipid from skin surface 3
• Use dispersible cream as a soap substitute for cleansing 3

If Inflammation Present

• Hydrocortisone (mild potency) applied 3-4 times daily is appropriate for affected areas 2
• Select the least potent topical corticosteroid preparation required to control symptoms 3

Symptomatic Relief

• Short course of nonsedating antihistamine may be tried for pruritus 1
• Never use sedating antihistamines, especially in elderly patients, as they do not reduce pruritus and may predispose to dementia 1, 2

When to Refer or Escalate

• Reassess in 1-2 weeks if no improvement with initial therapy 2
• Refer to dermatology if not responding to first-line management or if diagnosis remains uncertain 2
• Consider referral if diagnostic doubt exists, particularly to exclude scabies or other conditions 1, 4

Critical Red Flags Requiring Urgent Evaluation

• Multiple uniform "punched-out" erosions or vesiculopustular eruptions suggest eczema herpeticum, a medical emergency requiring immediate systemic antivirals 2
• Do not delay treatment of suspected eczema herpeticum—this is a true dermatologic emergency 2

Common Pitfalls to Avoid

• Do not assume the condition is purely benign without thoroughly examining for burrows (scabies) or signs of secondary infection 1, 4
• Avoid harsh detergents and fabric softeners when washing clothes 2
• Do not overlook secondary bacterial infection, which commonly complicates dry, itchy skin conditions 3