The handpalm rule can be used to estimate the percent of the body surface area (BSA) involved by a skin disorder.
The handpalm rule is based on the fact that the size of a patient's palm approximates 1% of the patient's body surface area.
percent body surface area involved by a skin disorder =
= (total number of the patient's handpalm areas needed to cover the involved areas)
• This is a gross estimate only. It works best for a limited number of handpalm-sized skin lesions on the trunk or proximal extremities. It performs worst on numerous small lesions or complex surfaces like the digits.
• It is adequate for deciding a gross question, such as whether or not 10% of the body surface area is involved. It might be inadequate for monitoring response to therapy.
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