General: common precancerous epidermal growths caused by sun exposure


Pathogenesis: UV radiation damages the DNA in keratinocytes, abnormal replication takes place and yields epidermal hyperplasia, dysplasia 


Risk factors: genetics, Caucasian, sun exposure (geographic region, occupation), lighter skin pigmentation


Physical exam: small, rough, scaling, reddish or brownish patch or papule, often on sun-exposed areas like the face, forearms


Differential: seborrheic keratoses (stuck on), carcinomas (larger, well-defined margins)


Histology: partial-thickness dysplasia of the epidermis, hyperkeratosis, parakeratosis 


Complications: indurated or stubborn actinic keratoses should be biopsied to rule out carcinoma, can progress to squamous cell carcinoma 


Treatment: (1) reduce sunlight exposure (hats, long-sleeves, SPF 30 sunscreen, avoid mid-day sun), (2) cryosurgery, could also use (3) topical 5-fluorouracil 5% twice daily for 2-3 weeks for multiple lesions (counsel patients that things will get worse over the next few weeks!)


References: AAD Basic Dermatology Curriculum, Dermatology by Bolognia et. al., Lookingbill and Mark's Principles of Dermatology, First Aid USMLE Step 1 2020, First Aid USMLE Step 2 CK