Scarlet Fever and White Blood Cell Count
Most patients with scarlet fever have normal white blood cell counts, and treatment with phenoxymethylpenicillin (Penicillin V) should be initiated immediately based on clinical presentation regardless of WBC values. 1, 2
WBC Findings in Scarlet Fever
- Normal WBC is typical: The majority of scarlet fever patients present with normal leukocyte counts, making WBC an unreliable marker for diagnosis or treatment decisions 3
- Mild elevation possible: When elevated, WBC counts are typically mild and non-specific 3
- C-reactive protein more useful: CRP elevation (average 2.4+) is more commonly observed than significant leukocytosis and may better reflect inflammatory response 3
Clinical Diagnosis Takes Priority
The diagnosis of scarlet fever is clinical and should not depend on laboratory values:
- Key diagnostic features: Distinctive macro-papular rash, strawberry tongue (86.3% of cases), severe throat redness, and angular stomatitis 3
- Age distribution: 82% of cases occur between ages 3-8 years, with average age of 5.8 years 3
- Fever pattern: Approximately 81.4% present with temperature above 38°C, typically lasting 2-5 days 3
Treatment Protocol
Immediate antibiotic therapy is mandatory regardless of WBC count or illness severity:
- First-line treatment: Phenoxymethylpenicillin (Penicillin V) should be prescribed immediately upon clinical diagnosis 1, 2, 4
- Alternative for penicillin allergy: Benzylpenicillin for severe cases or erysipelas 4
- Treatment goals: Antibiotics speed recovery, reduce contagious period, and prevent complications including acute rheumatic fever and glomerulonephritis 2, 4
Duration and Follow-up
- Early and prolonged therapy: Early initiation and adequate duration of penicillin treatment significantly reduces both early and late complications 5
- Post-treatment monitoring: Follow-up at 30 days post-discharge shows reduced carrier rates of beta-hemolytic streptococcus with appropriate antibiotic duration 5
- Reinfection risk: Approximately 6.7% of patients experience reinfection or relapse, emphasizing need for complete treatment course 3
Common Pitfalls to Avoid
- Do not wait for elevated WBC: Normal leukocyte count does not exclude scarlet fever or indicate milder disease requiring less aggressive treatment 3
- Do not delay treatment for cultures: Unlike many infections where antibiotic stewardship suggests waiting, scarlet fever requires immediate treatment based on clinical presentation 1, 2
- Do not undertreat based on severity: Even mild cases require full antibiotic course to prevent serious complications like rheumatic fever 2, 4