Folliculitis, Furuncles, and Carbuncles

Follicle Foes - Intro & IDs

Folliculitis, furuncles, and carbuncles represent a spectrum of pyodermas targeting hair follicles, ranging from superficial inflammation to deep, painful abscesses.

⭐ Most common causative organism for folliculitis, furuncles, and carbuncles is Staphylococcus aureus.

Bug's Life - Culprits & Catalysts

• Causative Organisms:
  • Staphylococcus aureus (most common; MSSA/MRSA)
  • Pseudomonas aeruginosa (hot tub folliculitis)
  • Other Gram-negatives
  • Fungi: Malassezia spp. (Pityrosporum folliculitis)
• Predisposing Factors:
  • Occlusion (e.g., tight clothes), hyperhidrosis
  • Skin trauma (shaving, epilation)
  • Topical corticosteroids (prolonged use)
  • Systemic: Diabetes, obesity, immunodeficiency
  • Nasal S. aureus carriage

⭐ Hot tub folliculitis, typically appearing 1-4 days after exposure, is most commonly caused by Pseudomonas aeruginosa.

Skin Showdown - Features & Feel

⭐ Carbuncles are deeper, larger, and more painful than furuncles, often involve multiple hair follicles, and are more likely to be associated with systemic symptoms like fever and chills.

Case Crackers - Diagnosis & DDx

• Diagnosis: Primarily clinical (morphology, distribution).
• Investigations:
  • Gram stain & culture: If recurrent, widespread, unresponsive, or MRSA suspected.

  ⭐ Gram stain and culture with antibiotic sensitivity testing are indicated for lesions that are recurrent, severe, or not responding to empirical therapy, especially to identify MRSA.

  • Biopsy: Rarely; for atypical cases, suspected fungal/herpetic folliculitis.
• Key Differentials: Acne vulgaris, hidradenitis suppurativa, ruptured epidermal cyst, insect bites, fungal folliculitis (Pityrosporum), herpetic folliculitis.

Healing Heroes - Rx & Recurrence Rx

Effective management hinges on infection type and severity. Surgical drainage is key for abscesses.

Management Algorithm:

⭐ Incision and Drainage (I&D) is the cornerstone of treatment for fluctuant furuncles and carbuncles, often providing immediate relief and cure.

• Systemic Antibiotics for Furuncles/Carbuncles: Indicated for significant surrounding cellulitis, systemic symptoms, immunosuppression, or difficult-to-drain areas (e.g., face).

  • Empiric for S. aureus: Dicloxacillin, cephalexin.
  • MRSA suspected/confirmed: TMP-SMX, clindamycin, doxycycline, linezolid.
    • 📌 Mnemonic for MRSA Rx: "Trim My Skin, Clean Deep Lesions" (TMP-SMX, Clindamycin, Doxycycline, Linezolid).

• Prevention of Recurrence:

  • Maintain good personal hygiene.
  • Avoid sharing personal items (towels, razors).
  • Use antibacterial soaps for recurrent infections.
  • Consider mupirocin ointment for nasal decolonization of S. aureus carriers in recurrent cases (e.g., 2% ointment intranasally bid for 5-7 days).

High‑Yield Points - ⚡ Biggest Takeaways

• Staphylococcus aureus is the primary pathogen for folliculitis, furuncles, and carbuncles.
• Furuncles: deep infection of one hair follicle; Carbuncles: coalescing furuncles, deeper, wider.
• Incision and Drainage (I&D) is mainstay treatment for fluctuant furuncles and carbuncles.
• Systemic antibiotics for carbuncles, extensive disease, or immunocompromised patients.
• Suspect MRSA in non-responsive cases; use TMP-SMX, clindamycin, or doxycycline.
• Hot tub folliculitis: caused by Pseudomonas aeruginosa, often on trunk.
• Diabetes mellitus is a key risk factor for severe/recurrent infections.