Cellulitis

Infectious Disease · ~7% of blueprint

Pathophysiology: Bacterial infection of the dermis & subcutaneous tissue (Strep pyogenes, Staph aureus).
Signs & Symptoms: Spreading erythema, warmth, swelling, tenderness; ± fever; poorly demarcated borders.
Gold Standard Diagnosis: Clinical diagnosis; cultures not routinely recommended.
First-line Treatment: Non-purulent: cephalexin (strep coverage); purulent/MRSA risk: TMP-SMX or doxycycline.

High-Yield Pearl

Sharply demarcated raised borders = erysipelas (superficial); purulence → cover MRSA.

Sources

Reviewed September 2026

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