Disseminated superficial actinic porokeratosis, or DSAP, is an inherited skin condition causing dry patches mainly on the arms and legs.
DSAP is a special type of inherited "sun spot" and is sometimes confused with actinic keratoses, but actinic keratoses are more likely to arise on the face and hands.
The tendency to DSAP is inherited as an autosomal dominant characteristic, which means on average half of the children of an affected parent will also have the tendency. However a certain amount of accumulated sun exposure and perhaps other factors such as immune suppression are needed to bring this tendency out.
