Disseminated superficial actinic porokeratosis (DSAP) is an uncommon skin condition that leads to reddish brown scaly spots. The spots are mostly seem on the arms and legs, but sometimes will show up on other sun-damaged skin. It is due to an abnormal sun sensitivity leading to pre-cancerous skin cells. It is not a serious condition.
Most cases are inherited, but some occur in people whose immune systems are not working well. DSAP will only show up after sun damage has already occurred, so it is usually seen only in fair skinned people mid-life and beyond. For some reason, mostly women are affected. Once a spot of DSAP forms, it may slowly enlarge to form a ring or circle. The spots seem to grow or itch after sun exposure.
The diagnosis is usually obvious to a trained Dermatologist, as there is a fine, thready rim on the edge (a 'coronoid lamellae'). Occasionally, a small shaving of skin is removed for biopsy analysis if there is any doubt. While DSAP is pre-cancerous, it is uncommon for it to develop into a true skin cancer. Sometimes the spots develop worrisome changes, such as redness, crusting or scaling and need to be biopsied.
Once DSAP has been diagnosed, the best thing one can do is avoid further sun damage by wearing long sleeves and using strong sunscreens. Unfortunately, treatment of DSAP is not very satisfactory. Creams such as topical retinoids, 5-fluorouracil and imiquimod offer some slight help. Cryosurgery may be used, but can lead to areas of hypopigmentation. Photodynamic therapy has been used with mixed results.
Most Dermatologists advise an exam for skin cancer once or twice a year. The largest and most suspicious spots can be frozen off with liquid nitrogen at that time.
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