These have a dark or blistered center. These lesions are frequently seen with erythema multiforme but not exclusively so. The Koebner phenomenon, also called the isomorphic response, refers to the appearance of lesions along a site of injury. This descriptive term may apply to a wide variety of disorders. The former fades as the skin is warmed the latter becomes more florid.
Serpiginous lesions wander as though following the track of a snake.
The patient with a scarlatiniform rash has innumerable small red papules that are widely and diffusely distributed. Note that the term scarlatiniform does not mean that the patient has scarlet fever, although by definition all patients with scarlet fever have a scarlatiniform rash. Patients with a variety of other conditions such as Kawasaki disease, viral infections, or drug reactions may have rashes with the same pattern. Patients with measles will have the rash but patients with Kawasaki disease, drug reactions, or other conditions may also have a morbilliform rash. The rash consists of macular lesions that are red and are usually 2-10 mm in diameter but may be confluent in places.