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Paronychia. (Photo contributor: Lawrence B. Stack, MD.)


The authors acknowledge the contributions of Daniel L. Savitt, Selim Suner, and Robert J. Tubbs to previous editions.

Clinical Summary

Cellulitis is a common skin or subcutaneous tissue infection with characteristic findings: erythema with poorly defined borders, edema, warmth, pain, and limitation of movement. Fever and constitutional symptoms may be present and are associated with bacteremia. Predisposing factors include trauma, lymphatic or venous stasis, immunodeficiency (including diabetes mellitus), and foreign bodies. Common organisms include group A β-hemolytic Streptococcus and Staphylococcus aureus in nonintertriginous skin, and gram-negative organisms or mixed flora in intertriginous skin and ulcerations. In immunocompromised hosts, Escherichia coli, Klebsiella species, Enterobacter species, and Pseudomonas aeruginosa may be present. There has been an increase in community-acquired methicillin-resistant S aureus (CA-MRSA), particularly in cellulitis associated with a cutaneous abscess. Differential diagnosis includes deep venous thrombosis (DVT), venous stasis, erythema nodosum, septic or inflammatory arthritis/bursitis, and allergic reactions.

Management and Disposition

Treatment of minor cases commonly consists of elevation, analgesia, and oral β-lactam antibiotics with reevaluation in 48 hours. The increase in CA-MRSA has prompted some, especially in highly endemic areas, to advocate coverage with trimethoprim/sulfamethoxazole, clindamycin, doxycycline, or other agents in addition to conventional β-lactam antibiotics. Admission and parenteral antibiotic administration may be necessary for immunocompromised or toxic-appearing patients or those who do not respond to outpatient therapy.


  1. Rapidly progressive cellulitis or one that progresses despite treatment with β-lactam antibiotics should raise suspicion for CA-MRSA or deeper infections such as fasciitis.

  2. Known risk factors for CA-MRSA include military personnel, prison inmates, and competitive sports players.

  3. Routine blood or leading-edge cultures in nontoxic patients are generally low yield.


Cellulitis. Cellulitis of the left leg characterized by erythema and mild swelling. (Photo contributor: Frank Birinyi, MD.)


Cellulitis. Cellulitis of the right lower extremity characterized by sharply demarcated erythema and edema. (Photo contributor: Robert Tubbs, MD.)

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