Atlas of pathophysiology, 2 Edition

Part II - Disorders

Skin Disorders

Folliculitis, furuncles, carbuncles

Folliculitis is a bacterial infection in the upper portion of a hair follicle that causes a papule, pustule, or erosion. The infection can be superficial (follicular impetigo or Bockhart's impetigo) or deep (sycosis barbae). Furuncles, also known as boils, affect the entire hair follicle and the adjacent subcutaneous tissue. Carbuncles are a group of interconnected furuncles.

With appropriate treatment, the prognosis for patients with folliculitis is good. The disorder usually resolves within 2 to 3 weeks. The prognosis for patients with carbuncles depends on the severity of the infection and the patient's physical condition and ability to resist infection.

Causes

·   Coagulase-positive Staphylococcus aureus (most common)

·   Klebsiella, Enterobacter, or Proteus organisms (gram-negative folliculitis in patients on long-term antibiotic therapy such as for acne)

·   Pseudomonas aeruginosa (thrives in warm environment with high pH and low chlorine content—“hot-tub folliculitis”)

Predisposing risk factors

·   Shaving, plucking, or waxing

·   Infected wound, poor hygiene

·   Chronic staphylococcus carrier state in nares, axillae, perineum, or bowel

·   Diabetes

·   Debilitation

·   Immunosuppressive therapy, defects in chemotaxis, hyperimmunoglobulinemia E syndrome

·   Tight clothes, friction

·   Living in a tropical climate

Pathophysiology

The affecting organism enters the body, usually at a break in the skin barrier such as a wound site. The organism then causes an inflammatory reaction within the hair follicle.

Staphylococcal infection commonly causes the abscess, which consists of a fibrin wall with surrounding inflamed tissues. This encloses a core of pus containing organisms and leukocytes.

Hematologic spread of infection is possible even from the smallest abscess and is enhanced by proteolytic enzymes produced by the staphylococcal organisms. This spread can result in pneumonia and infection of the heart valves, bones, and joints. Immunocompromised patients may develop fatal sepsis.

Signs and symptoms

Folliculitis

·   In children—papule or pustules on scalp, arms, or legs

·   In adults—papule or pustules on trunk, buttocks, legs, or face

Furuncles

·   Firm or fluctuant, painful nodules, commonly on neck, face, axillae, or buttocks

·   Nodules enlarge for several days, then rupture, discharging pus and necrotic material

·   After rupture, pain subsides (erythema and edema persist for days or weeks)

Carbuncles

·   Extremely painful, deep abscesses draining through multiple openings onto the skin surface, around several hair follicles

·   Fever and malaise

Diagnostic test results

·   Wound cultures and sensitivity test results show the offending organism.

·   Blood chemistry reveals elevated white blood cell count.

Treatment

·   Thorough cleaning of the infected area with antibacterial soap and water several times per day

·   Warm, wet compresses to promote vasodilation and drainage

·   Topical antibiotics, such as mupirocin ointment or clindamycin or erythromycin solution

Specific treatments

·   Extensive folliculitis: systemic antibiotics, such as a cephalosporin or dicloxacillin

·   Furuncles (ripe lesions):

§  warm, wet compresses

§  incision and drainage

§  systemic antibiotic therapy

·   Carbuncles:

§  incision and drainage

§  systemic antibiotic therapy

P.381

DISTINGUISHING FOLLICULITIS, FURUNCLES, AND CARBUNCLES

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