Bacterial Infections: Deep Folliculitis & Cellulitis
Infectious dermatology requires distinguishing between localized follicular inflammation and broader soft tissue infections.
Key Comparisons
| Condition | Pathophysiology | Clinical Features |
|---|---|---|
| Furuncle/Carbuncle | Deep follicular infection (S. aureus) | Painful, red nodule; Carbuncle = coalesced furuncles. |
| Cellulitis | Dermal/subcutaneous infection (S. pyogenes/S. aureus) | Spreading erythema, warmth, edema, ill-defined borders. |
| Erysipelas | Superficial dermal/lymphatic (S. pyogenes) | Bright red, raised, well-defined borders. |
Management Considerations
- Deep Folliculitis (Furuncles): Warm compresses may suffice for mild cases. I&D is the gold standard for fluctuant abscesses. Systemic antibiotics (e.g., Cephalexin, TMP-SMX) are indicated if cellulitis is present or if the lesion is large/multiple.
- Cellulitis: Requires systemic antibiotics covering *S. aureus* and *S. pyogenes*. Monitor for systemic signs (fever, chills, leukocytosis).
- Important Rule: Distinguish “true” cellulitis from mimics like Stasis Dermatitis, which is typically bilateral and chronic.
High-Yield Exam Pearl:
- Carbuncles: Often associated with S. aureus and commonly seen on the nape of the neck or back.
- Well-defined vs. Ill-defined: If the lesion is bright red and has sharply raised borders, it is likely Erysipelas; if the borders are flat and spread out, it is Cellulitis.