A 6-year-old girl from Delhi presents with her father complaining of multiple painful pustules and crusted lesions on her face and neck that began 5 days ago after she scratched a mosquito bite. The lesions are arranged in clusters and are spreading rapidly. On examination, there is regional lymphadenopathy (submandibular and cervical nodes are enlarged and tender). The father mentions that two other children in the neighbourhood have similar lesions. A culture from the pustule grows beta-haemolytic Gram-positive cocci in chains. What is the most appropriate first-line treatment?

Explanation

## Diagnosis & Management: Non-Bullous Impetigo with Regional Lymphadenopathy ### Clinical Diagnosis The patient presents with **non-bullous impetigo** caused by *Streptococcus pyogenes* (Group A Streptococcus), evidenced by: - **Pustules and honey-crusted erosions** (hallmark of non-bullous impetigo) - **Beta-haemolytic Gram-positive cocci in chains** (diagnostic for *S. pyogenes*) - **Regional lymphadenopathy** (impetigo impetiginosa — *S. pyogenes* impetigo with lymphangitis) - **Rapid spread** and **contagious nature** (explaining the cluster in the neighbourhood) - **Predisposing factor:** Trauma (mosquito bite scratch) ### Why Systemic Therapy Is Indicated **Key Point:** Although topical antibiotics are first-line for **localized, non-bullous impetigo without systemic signs**, this patient requires **systemic antibiotics** because of: 1. **Regional lymphadenopathy** (indicates lymphangitis — spread beyond the skin) 2. **Rapid progression** and **extensive lesions** 3. **Risk of complications:** Post-streptococcal glomerulonephritis (PSGN), acute rheumatic fever (ARF) — *S. pyogenes* impetigo carries this risk 4. **High contagiosity** in a community setting **High-Yield:** Impetigo with lymphangitis and regional lymphadenopathy is called **impetigo impetiginosa** and mandates systemic antibiotic therapy. ### First-Line Systemic Antibiotic Selection | Antibiotic | Indication | Dosing | Notes | |-------------|-----------|--------|-------| | **Amoxicillin-clavulanate** | Non-bullous impetigo (streptococcal or staphylococcal) | 375 mg TDS × 7 days | **First-line for mixed infections** (covers both *S. pyogenes* and *S. aureus*) | | **Cephalexin** | Alternative to amoxicillin-clavulanate | 500 mg QID × 7 days | Good for *S. aureus*; covers *S. pyogenes* | | **Penicillin V** | Pure *S. pyogenes* impetigo | 250 mg QID × 7 days | Excellent for *S. pyogenes* alone; less common in practice | | **Erythromycin** | Penicillin allergy | 250 mg QID × 7 days | Second-line; increasing resistance | **Clinical Pearl:** Although *S. pyogenes* is confirmed here, **amoxicillin-clavulanate is preferred** because: - It covers both *S. pyogenes* AND *S. aureus* (including MRSA in some regions) - In practice, mixed infections are common - It is the standard empiric choice for impetigo in India ### Why Other Options Are Incorrect **Topical mupirocin** (Option A): - Appropriate ONLY for **localized, non-bullous impetigo without systemic signs or lymphadenopathy** - This patient has **regional lymphadenopathy** → requires systemic therapy - Topical therapy alone would be inadequate and risks complications (PSGN, ARF) **Intravenous ceftriaxone** (Option C): - **Overkill** for uncomplicated impetigo - Reserved for **severe, invasive infections** (cellulitis, abscess, systemic toxicity) or immunocompromised patients - Unnecessary hospitalization and cost **Topical fusidic acid** (Option D): - Good for localized staphylococcal infections - **Inadequate for streptococcal impetigo with lymphangitis** - Topical therapy is insufficient when lymphadenopathy is present ### Management Summary ```mermaid flowchart TD A["Non-bullous Impetigo (S. pyogenes)"]:::outcome --> B{"Localized without lymphadenopathy?"}:::decision B -->|Yes| C["Topical mupirocin 2% TDS × 7–10 days"]:::action B -->|No| D{"Extensive or with lymphadenopathy?"}:::decision D -->|Yes| E["Oral amoxicillin-clavulanate 375 mg TDS × 7 days"]:::action D -->|Severe/invasive| F["IV ceftriaxone or hospitalize"]:::urgent E --> G["Review at 48–72 hrs"]:::action G --> H{"Improving?"}:::decision H -->|Yes| I["Continue to completion"]:::action H -->|No| J["Switch to alternative or IV therapy"]:::urgent ``` **Warning:** Do NOT use topical antibiotics alone in the presence of **lymphadenopathy, fever, or signs of systemic spread** — risk of serious complications (PSGN, ARF) if inadequately treated. ### Prevention of Complications - **Treat promptly** with systemic antibiotics to prevent PSGN and ARF - **Educate on hygiene:** Regular bathing, nail trimming, avoid scratching - **Isolate from other children** for 48 hours after starting antibiotics