Clinical Case Analysis: 2-Month-Old Female with 2-Week Paroxysmal Cough

1. Preliminary Diagnosis

• Age 2 months, unvaccinated — highest-risk demographic
• Gradual onset: initial dry cough → progressed to paroxysmal character (classic catarrhal → paroxysmal stage transition)
• 2-week illness duration consistent with paroxysmal stage
• Up to 15 coughing attacks/day with facial flushing and viscous sputum discharge
• Nocturnal apnea (~10 sec) and cyanosis — hallmark of severe infantile pertussis; infants often present with apnea/cyanosis rather than the classic whoop
• CBC findings: leukocytosis (15.4 × 10⁹/L) with marked lymphocytosis (75%) — pertussis toxin directly induces lymphocytosis, a classic laboratory hallmark
• Tachycardia (HR 132) and tachypnea (RR 48) suggest physiologic stress
• No fever, no hepatosplenomegaly — against systemic bacterial infection

"Severe and fatal disease is concentrated among infants, in whom pertussis may be manifested by spells of apnea and cyanosis, alone or in conjunction with coughing." — Goldman-Cecil Medicine

"Disease in infants younger than 6 months can be atypical with a short catarrhal stage, followed by gagging, gasping, bradycardia, or apnea as prominent early manifestations; absence of whoop." — Red Book 2021

2. Differential Diagnosis

3. Examination Plan

Confirmatory Tests for Pertussis

1. Nasopharyngeal PCR for B. pertussis — gold standard; sensitive, remains positive for several weeks even after antibiotic initiation; can distinguish B. pertussis, B. parapertussis, and B. bronchiseptica
2. Nasopharyngeal culture (Regan-Lowe or Bordet-Gengou medium) — sensitivity ~50%; best yield in early catarrhal/early paroxysmal stage before antibiotics
3. Serology (anti-pertussis toxin IgG/IgA) — useful later in illness; must distinguish acute response from vaccine antibodies (irrelevant here since unvaccinated)
4. DFA (direct fluorescent antibody) — less sensitive, not recommended as sole test

Baseline & Monitoring

1. Repeat CBC with differential — monitor degree of lymphocytosis (extreme lymphocytosis >100 × 10⁹/L is a predictor of fatal pulmonary hypertension in infants)
2. Chest X-ray — assess for "shaggy heart" sign, pneumonia, atelectasis, or pneumothorax
3. Pulse oximetry (continuous) — mandatory given apnea episode
4. Arterial blood gas / capillary blood gas — assess oxygenation and ventilatory status
5. Blood glucose — pertussis toxin enhances insulin secretion → hypoglycemia risk
6. Echocardiography — if lymphocyte count markedly elevated, to screen for pulmonary hypertension
7. Blood culture — to exclude secondary bacterial sepsis
8. Electrolytes, BMP — baseline, particularly if poor oral intake

4. Treatment Plan

Hospitalization

• Continuous pulse oximetry and cardiorespiratory monitoring (given documented apnea)
• Suction available at bedside; minimize stimulation triggering paroxysms
• Supplemental oxygen as needed to maintain SpO₂ ≥ 95%
• Small, frequent feeds; consider nasogastric feeding if feeding compromised by coughing

Antibiotic Therapy

"Given the association of erythromycin with infantile hypertrophic pyloric stenosis, we recommend azithromycin when available." — Rosen's Emergency Medicine

Supportive Care

• Avoid antitussives — no proven benefit; may be harmful
• Corticosteroids / salbutamol — not recommended; no evidence of benefit
• IV fluids — if oral intake inadequate
• For apnea/severe hypoxia: respiratory support (high-flow oxygen, CPAP, or mechanical ventilation if necessary)
• Leukodepletion / exchange transfusion — consider if extreme leukocytosis (>100 × 10⁹/L) with developing pulmonary hypertension

5. Prophylaxis and Anti-Epidemic Measures

A. Chemoprophylaxis for Close Contacts

• Azithromycin 500 mg on day 1, then 250 mg on days 2–5 (adults)
• Infants and young children: weight-based azithromycin
• Initiated within 21 days of last exposure to be effective
• Most effective when begun before symptom onset

"Chemoprophylaxis is recommended for individuals exposed within the preceding 3 weeks, high-risk persons, infants, and other individuals who have not been immunized." — Goldman-Cecil Medicine

B. Isolation

• Respiratory droplet isolation during hospitalization
• Infected child should be excluded from community settings until:
  • 5 days of appropriate antibiotic therapy completed, OR
  • 21 days from symptom onset if untreated

C. Vaccination (Long-term Prevention)

• DTaP vaccine series: begin as soon as clinically stable — at 2, 4, and 6 months of age, with boosters at 15–18 months and 4–6 years
• Tdap for all close adult contacts (cocooning strategy) — particularly household members and caregivers
• Maternal Tdap during pregnancy (ideally 27–36 weeks gestation) for future pregnancies — provides passive IgG protection to infant in first 3 months, the most vulnerable period

D. Notification

• Mandatory disease notification to public health authorities — pertussis is a notifiable disease in most jurisdictions
• Contact tracing in childcare, family, and healthcare settings
• Epidemiological investigation to identify the source case (often an adult with mild or unrecognized illness)

E. Health Education

• Educate caregivers on the importance of vaccination adherence
• Stress that adults and older siblings can be asymptomatic carriers or have only mild cough, serving as the source of infection for unvaccinated infants