Cellulitis and erysipelas are skin infections that develop as a result of bacterial entry via breaches in the skin barrier. The incidence is about 200 cases per 100,000 patient-years . Cellulitis is observed most frequently among middle-aged individuals and older adults, while erysipelas occurs in young children and older adults [2,3].
The clinical manifestations, diagnosis, microbiology, and treatment of cellulitis and erysipelas will be reviewed here. Issues related to special forms of cellulitis are discussed separately. (See "Clinical manifestations, diagnosis, and management of diabetic infections of the lower extremities" and "Initial management of animal and human bites" and "Soft tissue infections due to dog and cat bites" and "Soft tissue infections following water exposure" and "Orbital cellulitis".)
Cellulitis and erysipelas manifest as areas of skin erythema, edema, and warmth. They differ in that erysipelas involves the upper dermis and superficial lymphatics, whereas cellulitis involves the deeper dermis and subcutaneous fat. As a result, erysipelas has more distinctive anatomic features than cellulitis; erysipelas lesions are raised above the level of surrounding skin, and there is a clear line of demarcation between involved and uninvolved tissue . Classic descriptions of erysipelas note "butterfly" involvement of the face. Involvement of the ear (Milian's ear sign) is a distinguishing feature for erysipelas, since this region does not contain deeper dermis tissue. In addition, patients with erysipelas tend to have acute onset of symptoms with systemic manifestations including fever and chills; patients with cellulitis tend to have a more indolent course with development of localized symptoms over a few days' time. Cellulitis may present with or without purulent drainage or exudate .
The lower extremities are the most common site of infection for both erysipelas and cellulitis (picture 1A-B) [2,6]. Other forms of cellulitis include periorbital cellulitis, abdominal wall cellulitis (in morbidly obese individuals), buccal cellulitis (due to Streptococcus pneumoniae and, prior to the conjugate vaccine era, Haemophilus influenzae type b) and perianal cellulitis (due to group A beta-hemolytic Streptococcus) [7,8]. (See "Orbital cellulitis".)
Rarely, infections involving the medial third of the face (ie, the areas around the eyes and nose) can be complicated by septic cavernous thrombosis, since the veins in this region are valveless (figure 1). (See "Septic dural sinus thrombosis".)