Definition
Cellulitis
- A diffuse, spreading bacterial skin infection that involves the subcutaneous tissues
- Typically occurs in areas where the skin integrity has been compromised
- More commonly affects the lower extremities in adults, and the face and neck in children
- May also result from blood-borne spread of infection to the skin and subcutaneous tissues
- Commonly caused by beta-hemolytic streptococci and Staphylococcus aureus
- Infection due to streptococci is rapidly spreading because of streptokinase while that of S aureus is localized
- Consider Methicillin-resistant S aureus (MRSA) in patients with recurrent cellulitis, refractory to treatment, or exposed to a hospital or nursing facility
- Can also be caused by Streptococcus pneumoniae, Haemophilus influenzae, Gram-negative bacilli and anaerobes
Erysipelas
- A type of cellulitis with margins that are sharply demarcated, involves the epidermis and superficial lymphatics
- Also referred to as St Anthony’s fire
- Onset of symptoms is acute with accompanying systemic manifestations whereas cellulitis has an indolent course
- More commonly caused by beta-hemolytic streptococci
Etiology
Cellulitis
- Etiology of cellulitis remains unidentified in most patients and treatment needs to be empiric based on clinical presentation
Uncomplicated Cellulitis
- Beta-hemolytic streptococcal etiology in 90% of infections but S aureus is difficult to exclude especially if mixed infection occurs
Complicated Cellulitis
- Group A streptococci, S aureus, Enterobacteriaceae and anaerobes
Signs and Symptoms
- Rapidly spreading area of acute inflammation of the dermis and subcutaneous tissue
- Typically unilateral and common in the lower extremities
- “Butterfly” involvement of the face and of the ears (Milian’s ear sign) is suggestive of erysipelas
- Lymphangitis and inflammation of the regional lymph nodes may occur
- Appears as red, swollen, and painful area of skin that is warm and tender to touch
- Patient may have malaise, fever and chills
Risk Factors
- Obesity
- Diabetes mellitus (DM) and malignancy
- Immunosuppression
- Alcoholism
- Intravenous (IV) drug abuse
- Atopic dermatitis
- Previous cutaneous damage (eg animal bites, abrasions, wounds, etc)
- Surgery
- Edema from venous insufficiency or lymphatic obstruction
- Water exposure