1. What is a Body Surface Area Calculator for Psoriasis?

Definition: This calculator estimates the percentage of body surface area (BSA) affected by psoriasis using the palm method.

Purpose: It helps dermatologists and patients assess psoriasis severity by quantifying the extent of skin involvement.

2. How Does the Calculator Work?

The calculator uses the palm method formula:

Where:

• \( \%BSA \) — Percentage of body surface area affected
• Each body region is estimated as a percentage of total BSA
• 1 palm ≈ 1% of total body surface area

Explanation: The affected areas of different body parts are summed to get the total percentage of BSA involved.

3. Importance of BSA Calculation in Psoriasis

Details: BSA assessment helps determine disease severity, guide treatment decisions, and monitor treatment response over time.

4. Using the Calculator

Tips: Enter the estimated percentage affected for each body region. Typical maximum values:

• Head: 9%
• Each arm: 9% (total 18% for both arms)
• Trunk: 36% (front and back)
• Each leg: 18% (total 36% for both legs)

5. Frequently Asked Questions (FAQ)

Q1: What is the palm method?
A: The palm method uses the patient's palm (including fingers) as approximately 1% of their total body surface area for estimation.

Q2: How accurate is this method?
A: While not as precise as more complex methods, it provides a quick, practical estimate suitable for clinical use.

Q3: What BSA percentage indicates severe psoriasis?
A: Generally, >10% BSA involvement is considered moderate to severe psoriasis.

Q4: Should I include unaffected areas?
A: No, only include skin areas with active psoriasis lesions.

Q5: How often should BSA be measured?
A: Regular assessments (e.g., every 3-6 months) help track disease progression and treatment effectiveness.