Folliculitis, Furuncles, and Carbuncles

Folliculitis, Furuncles, and Carbuncles

Folliculitis, Furuncles, and Carbuncles

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Follicle Foes - Intro & IDs

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

FeatureFolliculitisFuruncle (Boil)Carbuncle
DepthSuperficial/Deep follicleDeep follicleDeeper, subcutaneous tissue
StructuresHair follicle ostium/unitEntire follicle, adjacent dermisMultiple follicles, subcutaneous
No. of FolliclesSingle/MultipleSingleMultiple, coalescing
Key FeaturesFollicular pustules/papulesTender, firm, red noduleBroad, swollen, draining lesion; systemic sx often

⭐ 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

FeatureFolliculitisFuruncle (Boil)Carbuncle
AppearanceSuperficial pustules/papules (S); Deeper, tender nodules (D)Single, deep, tender nodule/pustuleMultiple interconnected furuncles, draining sinuses
Size1-5 mm1-2 cm>2 cm, often 3-10 cm
PainMild (S); Moderate (D)Moderate to SevereSevere
Systemic SxRareRareOften (fever, malaise)
Common SitesHairy areas (scalp, beard, axillae, buttocks)Hairy, friction-prone areasNape, back, thighs

⭐ 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.

Practice Questions: Folliculitis, Furuncles, and Carbuncles

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Flashcards: Folliculitis, Furuncles, and Carbuncles

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Streptococcus pyogenes may present with "honeycomb-like" crusts on the skin known as non-_____ impetigo

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Streptococcus pyogenes may present with "honeycomb-like" crusts on the skin known as non-_____ impetigo

bullous

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