Types of Streptococcal Rashes
Streptococcal bacteria cause four distinct types of rashes: impetigo (with bullous and nonbullous variants), erysipelas, cellulitis, and scarlet fever (scarlatiniform rash). 1
Primary Streptococcal Rash Types
1. Impetigo
Impetigo presents in two distinct forms, both caused by β-hemolytic streptococci and/or S. aureus:
Nonbullous Impetigo (70% of cases)
- Begins as papules that rapidly evolve into vesicles surrounded by erythema 1
- Progresses to pustules that enlarge and break down over 4-6 days 1
- Forms characteristic thick, honey-colored crusts resembling lacquer 1, 2
- Most commonly affects the face and extremities 1
- Typically occurs in children aged 2-5 years 1
Bullous Impetigo (30% of cases)
- Caused exclusively by S. aureus 2
- Starts as superficial vesicles that rapidly enlarge to form flaccid bullae filled with clear yellow fluid 1
- Fluid later becomes darker, more turbid, and sometimes purulent 1
- Bullae rupture leaving thin brown crusts 1
- More likely to affect intertriginous areas (skin folds) 2
Ecthyma is a deeply ulcerated variant of impetigo that heals slowly and leaves depigmented areas 1
2. Erysipelas
- Presents as a fiery red, tender, painful plaque with sharply demarcated edges 1
- Commonly caused by streptococcal species, usually Streptococcus pyogenes 1
- S. aureus rarely causes erysipelas 1
- Involves the dermis or hypodermis with associated high fever 3
- Most facial infections attributed to Group A Streptococcus, with increasing percentage of lower extremity infections from non-GAS 1
- Venous insufficiency or lymphedema are important predisposing factors 3
3. Cellulitis
- Acute bacterial infection of the dermis and subcutaneous tissue 1
- Causes warmth, erythema, pain, and lymphangitis 1
- Frequently accompanied by systemic upset with fever and elevated white blood cell count 1
- Streptococci cause diffuse, rapidly spreading infection; staphylococcal cellulitis is typically more localized 1
- Most commonly affects lower extremities but can occur elsewhere 1
- Cellulitis associated with furuncles, carbuncles, or abscesses is usually caused by S. aureus, while diffuse cellulitis without a defined portal is most commonly streptococcal 1
4. Scarlet Fever (Scarlatiniform Rash)
- Caused by streptococcal pyrogenic exotoxins produced by certain strains of Group A streptococci 4
- Characterized by a sandpaper-like rash in children with fever 5
- Accompanies streptococcal pharyngitis with typical features including sudden onset sore throat, fever, tonsillopharyngeal erythema, and tender anterior cervical lymphadenopathy 4
- Additional findings may include beefy red swollen uvula and petechiae on the palate 4
- Primarily affects children between 5-15 years of age 4
Important Clinical Distinctions
Common Pitfall: Arcanobacterium haemolyticum can produce a scarlet fever-like rash with pharyngitis, particularly in teenagers and young adults, though rarely recognized in the United States 1, 4. This mimics streptococcal scarlatiniform rash but requires different consideration.
Key Diagnostic Point: Regional lymphadenitis may occur with impetigo, but systemic symptoms are usually absent, distinguishing it from more invasive infections 1. In contrast, erysipelas and cellulitis typically present with systemic symptoms including fever 1, 3.
Treatment Implications: The type of rash determines management—impetigo may be treated topically with mupirocin for limited lesions 1, erysipelas requires penicillin 1, cellulitis needs penicillinase-resistant antibiotics or first-generation cephalosporins 1, and scarlet fever is treated as streptococcal pharyngitis with appropriate antibiotics 6.