10.1 Exanthems, Meningitis, Sepsis & Febrile Seizures
Key Takeaways
- Simple febrile seizures last <15 minutes, are generalized, and occur once in 24 hours; they do not require routine EEG or neuroimaging.
- Measles presents with Cough, Coryza, Conjunctivitis, and Koplik spots prior to a cephalocaudal maculopapular rash.
- Bacterial meningitis in neonates is most commonly caused by Group B Streptococcus, E. coli, and Listeria monocytogenes; empiric therapy includes Ampicillin and Cefotaxime or Gentamicin.
- Cerebrospinal fluid (CSF) in bacterial meningitis shows elevated opening pressure, >1000 WBCs with neutrophil predominance, elevated protein, and low glucose.
- In Saudi Arabia, the National Immunization Schedule provides the MMR vaccine at 12 and 18 months, significantly reducing the incidence of viral exanthems.
Pediatric Infectious Diseases and Febrile Seizures
Pediatric infections and their complications represent a significant portion of the SMLE, requiring candidates to rapidly differentiate clinical presentations, interpret diagnostic findings, and initiate appropriate empirical management. This section explores viral exanthems, central nervous system infections, pediatric sepsis, and febrile seizures.
1. Pediatric Exanthems (Childhood Rashes)
The classic childhood exanthems share overlapping features but possess distinct prodromal symptoms and rash morphologies. In Saudi Arabia, robust adherence to the National Immunization Schedule (e.g., MMR given at 12 and 18 months) has reduced the incidence of measles and rubella, though outbreaks still occur and require prompt public health reporting to the Saudi Ministry of Health (MOH).
| Disease | Agent | Prodrome | Rash Characteristics | Classic Pearl |
|---|---|---|---|---|
| Measles (Rubeola) | Paramyxovirus | High fever, Cough, Coryza, Conjunctivitis. | Cephalocaudal maculopapular spread (starts at hairline). | Koplik spots (white spots on buccal mucosa). |
| Rubella (German Measles) | Togavirus | Low-grade fever, tender postauricular and suboccipital lymphadenopathy. | Pink maculopapular rash starting on face, spreads down quickly. | Forchheimer spots; devastating congenital defects (TORCH). |
| Roseola (Exanthem Subitum) | HHV-6 | 3-5 days of high fever (>40°C), well-appearing. | Blanching maculopapular rash appears after fever resolves. | Most common cause of febrile seizures in infants. |
| Erythema Infectiosum | Parvovirus B19 | Mild viral symptoms. | "Slapped cheek" rash on face, followed by reticular lacy rash on trunk/extremities. | Aplastic crisis in sickle cell disease; fetal hydrops. |
| Varicella (Chickenpox) | VZV | Fever, malaise. | Vesicular rash described as "dew drop on a rose petal." Lesions in multiple stages. | Highly contagious; airborne precautions. |
Clinical Management
Most viral exanthems are self-limiting and require supportive care (hydration, antipyretics). However, measles may require Vitamin A supplementation, which has been shown to reduce morbidity and mortality, particularly in malnourished populations or those with severe complications like pneumonia or encephalitis.
2. Pediatric Meningitis and Sepsis
Acute bacterial meningitis is a medical emergency. The epidemiology of causative organisms varies by age, dictating empiric antibiotic choices.
- Neonates (0-28 days): Group B Streptococcus, E. coli, Listeria monocytogenes. (Empiric: Ampicillin + Cefotaxime or Gentamicin). Ceftriaxone is avoided in neonates due to biliary sludging and kernicterus risk.
- Children (1 month - 18 years): Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b. (Empiric: Ceftriaxone + Vancomycin).
Diagnostic Interpretation: Lumbar Puncture (CSF Analysis)
A lumbar puncture (LP) must be performed in suspected meningitis unless contraindicated (e.g., focal neurological deficit, papilledema, hemodynamic instability, or severe thrombocytopenia). If LP is delayed, antibiotics must be administered immediately after drawing blood cultures.
| Parameter | Normal | Bacterial | Viral (Aseptic) | Tuberculous (TB) |
|---|---|---|---|---|
| Opening Pressure | 5-20 cm H2O | Elevated (>25) | Normal / Slightly elevated | Elevated |
| WBC Count | 0-5 /mm³ | >1000 /mm³ | 100-1000 /mm³ | 100-500 /mm³ |
| Cell Predominance | Lymphocytes | Neutrophils (PMNs) | Lymphocytes | Lymphocytes |
| Protein | 15-45 mg/dL | High (>100 mg/dL) | Normal or slightly high | Very High (often >100) |
| Glucose | 50-80 mg/dL (2/3 of serum) | Low (<40 mg/dL) | Normal | Low |
Pediatric Sepsis
Pediatric sepsis requires a high index of suspicion. Early signs include tachycardia, tachypnea, and altered perfusion (capillary refill > 2 seconds, mottled skin). Hypotension is a late and ominous sign of decompensated shock in children. Initial management follows the "golden hour" principles: establish IV/IO access within 5 minutes, administer fluid boluses (20 mL/kg isotonic crystalloid) up to 60 mL/kg unless hepatomegaly/crackles develop, and administer broad-spectrum antibiotics within 1 hour.
3. Febrile Seizures
Febrile seizures are the most common neurological disorder in infants and young children, affecting 2-5% of children between 6 months and 5 years of age. They occur in the setting of a fever (>38°C) without intracranial infection or defined metabolic derangement.
Simple vs. Complex Febrile Seizures
Differentiation is crucial as it dictates the need for further workup and the recurrence risk.
- Simple Febrile Seizures: Last less than 15 minutes, generalized (tonic-clonic), and do not recur within a 24-hour period. Children return to baseline rapidly.
- Complex Febrile Seizures: Last more than 15 minutes, focal onset or focal features during the seizure, or recur within 24 hours.
Management and Counseling
For simple febrile seizures, routine EEG, neuroimaging (CT/MRI), or lumbar puncture are not indicated unless there are red flags (e.g., meningeal signs, incomplete Hib/Strep pneumo immunization). The core of management is parental reassurance. Parents should be educated that simple febrile seizures do not cause brain damage, intellectual disability, or learning difficulties. The risk of developing epilepsy is only slightly higher than the general population (1-2%). Prophylactic antiepileptics or continuous antipyretics do not prevent recurrence and are not recommended.
A 4-year-old boy is brought to the emergency department in Riyadh after experiencing a generalized tonic-clonic seizure that lasted 5 minutes. The mother reports he has had a high fever and a runny nose since yesterday. He is fully immunized according to the Saudi National Immunization Schedule. On examination, his temperature is 39.5°C, and he is alert and playful. There are no signs of meningeal irritation. Which of the following is the most appropriate next step in management?
A 10-month-old infant presents with a 3-day history of high fever up to 40°C. The infant appeared relatively well during the febrile period despite the high temperature. Today, the fever abruptly resolved, and the mother noted the appearance of a blanching, pink maculopapular rash on the infant's trunk that is spreading to the extremities. Which of the following is the most likely diagnosis?
A 2-week-old neonate is admitted to the neonatal intensive care unit with poor feeding, lethargy, and temperature instability. A lumbar puncture is performed, revealing an opening pressure of 28 cm H2O, a WBC count of 1500/mm³ with 90% neutrophils, a protein level of 120 mg/dL, and a glucose level of 20 mg/dL. Which of the following empiric antibiotic regimens is most appropriate for this patient?