• An acute spreading skin infection that may go deep, involving the subcutaneous tissues
• Typically occurs in areas where the skin integrity has been compromised
• May also result from blood-borne spread of infection to the skin & subcutaneous tissues

Erysipelas

• A type of cellulitis w/ sharply demarcated margins involving the epidermis & superficial lymphatics
• Onset of symptoms is acute whereas cellulitis has an indolent course
• More commonly caused by beta-hemolytic streptococci

• Commonly caused by beta-hemolytic streptococci & Staphylococcus aureus in adults, & Haemophilus influenzae type B in patients <3 years
  
  • Infection due to streptococci is rapidly spreading because of streptokinase while that of staphylococci is localized
  • Consider Methicillin-resistant S aureus (MRSA) in patients w/ recurrent cellulitis, or refractory to treatment 

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, Staphylococcus aureus, H influenzae B, Enterobacteriaceae & anaerobes

• Rapidly spreading area of acute inflammation of the dermis & subcutaneous tissue
• Lymphangitis & inflammation of the regional lymph nodes may occur
• Area is usually tender, erythematous & warm to the touch
• Patient may have malaise, fever & chills

• Obesity
• Diabetes mellitus & malignancy
• Immunocompromise
• Previous cutaneous damage
• Edema from venous insufficiency or lymphatic obstruction