Disease
Cellulitis
Spreading skin and subcutaneous infection
sell-yoo-LY-tis
High-yield clue
Warm, tender, spreading erythema with indistinct borders is the classic cellulitis recognition clue.
Overview
An acute spreading infection of the deep dermis and subcutaneous tissue, studied for its classic warm, tender, poorly demarcated erythema. It matters as the common benign end of the skin-infection spectrum that students contrast with limb-threatening deeper infections.
Classification
- Skin and soft-tissue syndrome
- Non-purulent (streptococcal) vs purulent (staphylococcal) patterns
- Superficial dermal vs deeper fascial contrast
- Community vs MRSA-associated framing
Lab & identification clues
- Clinical erythema, warmth, swelling, tenderness vocabulary
- Ill-defined non-elevated borders (vs sharply raised erysipelas) description
- Purulence/abscess suggesting Staphylococcus aureus
- Blood cultures usually low-yield concept
Associations
- Skin-barrier breaks: cuts, tinea, ulcers as entry points
- Streptococcus pyogenes and Staphylococcus aureus most common
- At-risk framing: edema, diabetes, venous insufficiency
- Distinction from rapidly progressive necrotizing infection
Commonly confused with
- Erysipelas
- Necrotizing fasciitis (early)
Your notes
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.