USMLE Guide: Common Pediatric Infections

An Informative Guide for usmle step 1 Preparation

Introduction

This guide aims to provide a comprehensive overview of common pediatric infections, which is essential knowledge for the United States Medical Licensing Examination (USMLE) Step 1. Familiarity with the etiology, clinical presentation, diagnosis, treatment, and prevention of these infections is crucial for medical students and professionals alike. This guide will cover several frequently encountered pediatric infections, including viral, bacterial, and fungal infections.

Table of Contents

1. Viral Infections
   • Respiratory Syncytial Virus (RSV)
   • Varicella-Zoster Virus (VZV)
   • Human Parainfluenza Virus (HPIV)
2. Bacterial Infections
   • Streptococcus pneumoniae
   • Haemophilus influenzae type b (Hib)
   • Group A Streptococcus (GAS)
3. Fungal Infections
   • Candidiasis
   • Tinea infections
4. Conclusion

Viral Infections

Respiratory Syncytial Virus (RSV)

• Etiology: RSV is a negative-sense, single-stranded RNA virus belonging to the Paramyxoviridae family.
• Clinical Presentation: RSV commonly causes bronchiolitis in infants and young children, characterized by cough, wheezing, and respiratory distress.
• Diagnosis: Clinical presentation, direct immunofluorescence assay, and viral culture can aid in the diagnosis.
• Treatment: Supportive care, including hydration, oxygen therapy, and nebulized bronchodilators, is the mainstay of management. Ribavirin may be considered in severe cases.
• Prevention: Palivizumab, a monoclonal antibody, can be administered to high-risk infants to prevent severe RSV infection.

Varicella-Zoster Virus (VZV)

• Etiology: VZV is a double-stranded DNA virus belonging to the Herpesviridae family.
• Clinical Presentation: Primary infection causes varicella (chickenpox), characterized by vesicular rash, fever, and malaise. Reactivation later in life leads to herpes zoster (shingles) with a dermatomal distribution.
• Diagnosis: Clinical presentation, viral culture, and polymerase chain reaction (PCR) can assist in diagnosis.
• Treatment: Supportive care, analgesics, and antiviral therapy (acyclovir, valacyclovir, or famciclovir) are used when indicated.
• Prevention: Varicella vaccine is highly effective in preventing primary infection. Zoster vaccine is recommended for individuals aged 50 years and older.

Human Parainfluenza Virus (HPIV)

• Etiology: HPIV is a negative-sense, single-stranded RNA virus from the Paramyxoviridae family.
• Clinical Presentation: HPIV commonly causes croup (laryngotracheobronchitis) in children, presenting with barking cough, stridor, and hoarseness.
• Diagnosis: Clinical presentation, viral culture, and PCR can aid in diagnosis.
• Treatment: Supportive care, including hydration, humidified air, and glucocorticoids, is the mainstay of management. In severe cases, nebulized epinephrine may be used.
• Prevention: No specific vaccine is available for HPIV.

Bacterial Infections

Streptococcus pneumoniae

• Etiology: S. pneumoniae is a gram-positive encapsulated diplococcus.
• Clinical Presentation: S. pneumoniae causes a wide range of infections, including pneumonia, meningitis, otitis media, and sinusitis.
• Diagnosis: Clinical features, blood cultures, and cerebrospinal fluid analysis aid in diagnosis.
• Treatment: antibiotic therapy depends on the site of infection but often includes penicillin or amoxicillin. Vaccination with the pneumococcal conjugate vaccine (PCV13) is recommended.
• Prevention: PCV13 and pneumococcal polysaccharide vaccine (PPSV23) are used for prevention.

Haemophilus influenzae type b (Hib)

• Etiology: Hib is a gram-negative coccobacillus.
• Clinical Presentation: Hib commonly causes meningitis, epiglottitis, pneumonia, and cellulitis in children.
• Diagnosis: Clinical presentation, blood cultures, and cerebrospinal fluid analysis help in diagnosis.
• Treatment: Antibiotic therapy, typically with ceftriaxone or cefotaxime, is used. Vaccination with the Hib conjugate vaccine is highly effective in prevention.
• Prevention: Hib conjugate vaccine is recommended for all children.

Group A Streptococcus