Sandpaper-Like Rash: Scarlet Fever
A sandpaper-like rash is the classic sign of scarlet fever, caused by Group A Streptococcus (Streptococcus pyogenes) producing pyrogenic exotoxins. 1, 2
Primary Diagnosis: Scarlet Fever
Scarlet fever presents with a distinctive erythematous, sandpaper-textured rash caused by streptococcal superantigens (SAgs) that overstimulate the immune system. 1, 2 This is a toxin-mediated disease, not a direct bacterial invasion of the skin, which explains the characteristic rough texture. 2
Key Clinical Features to Identify
- Sandpaper texture: The rash feels rough to touch, like fine-grade sandpaper, and is erythematous 1, 2
- Distribution: Typically begins on trunk and spreads to extremities, with accentuation in skin folds (groin, axillae) 3
- Associated symptoms: High fever, sore throat (streptococcal pharyngitis), and the pathognomonic "strawberry tongue" or "raspberry tongue" 1
- Timing: Rash appears 1-2 days after onset of fever and pharyngitis 1
- Facial involvement: Characteristic facial flushing with circumoral pallor 3
Critical Differential Diagnoses
While scarlet fever is the classic cause, other conditions must be excluded:
- Kawasaki disease: Can present with erythematous rash and strawberry tongue, but requires fever ≥5 days plus additional criteria (conjunctivitis, mucositis, extremity changes, lymphadenopathy) 3
- Staphylococcal toxic shock syndrome: Presents with diffuse erythroderma and systemic toxicity, but lacks the sandpaper texture 3
- Drug reactions: May cause maculopapular or scarlatiniform eruptions, but history of recent medication initiation is key 3
- Viral exanthems: Typically lack the sandpaper texture and associated pharyngitis 3
Diagnostic Approach
Obtain throat culture or rapid antigen detection test for Group A Streptococcus, along with anti-streptolysin-O (ASO) titers if diagnosis is uncertain. 4 The clinical presentation is often sufficient for diagnosis when the classic triad of sandpaper rash, pharyngitis, and strawberry tongue is present. 1
Laboratory Evaluation
- Throat culture/rapid strep test: Primary diagnostic tool for confirming streptococcal infection 4
- Complete blood count: May show leukocytosis 3
- Inflammatory markers: Elevated ESR and CRP support diagnosis but are nonspecific 3
Management Priority
Immediate antibiotic therapy is critical to prevent serious sequelae including acute rheumatic fever, post-streptococcal glomerulonephritis, and endocarditis. 1
Treatment Protocol
- First-line: Penicillin (500 mg QID) or amoxicillin (500 mg TID) for 10 days 3
- Penicillin allergy: Cephalexin, clindamycin, or azithromycin 3
- Supportive care: Antipyretics for fever, adequate hydration 3
Critical Pitfall
Do NOT delay antibiotic treatment waiting for culture results when clinical presentation is classic—early treatment reduces duration, prevents complications, and limits community spread. 1 The window for preventing rheumatic fever closes after 9 days from symptom onset. 3
Complications to Monitor
- Acute rheumatic fever: Can develop 2-3 weeks after untreated infection, presenting with carditis, polyarthritis, chorea, or subcutaneous nodules 3
- Post-streptococcal glomerulonephritis: Presents with hematuria, edema, and hypertension 1-2 weeks after infection 1
- Invasive streptococcal disease: Rare but serious, including necrotizing fasciitis or toxic shock syndrome 3
Special Considerations
Recent resurgence of scarlet fever in multiple geographic regions (particularly Europe and Asia) has been documented in the post-COVID-19 pandemic period, with increased virulence of certain strains. 1, 2 Clinicians should maintain high index of suspicion even in regions where scarlet fever was previously uncommon.