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An 8-week-old male infant presented with seizures (abnormal eye movements and posturing). Two weeks previously, he presented with a cough diagnosed as pertussis by nasopharyngeal aspirate PCR, and he received oral erythromycin for 7 days. Neither he nor his parents had received recent pertussis immunisation. At this presentation, nasopharyngeal aspirate PCR remained positive for Bordetella pertussis and was negative for other viruses including influenza. Additional investigations showed a lymphocytosis 18.2×109/l, normal inflammatory markers and sterile blood cultures. The cerebrospinal fluid (CSF) was acellular with normal glucose and elevated protein 1.2 g/l and was sterile on culture. CSF PCR for herpes simplex virus and enterovirus were negative. MRI of the brain showed caudate nucleus enhancement suggesting encephalitis (figure 1), a rare complication of pertussis although abnormal MRI is an unusual finding. Subsequent CSF PCR for pertussis was negative: the usual finding in pertussis encephalopathy. He received azithromycin for 5 days and made an uncomplicated recovery with normal neurodevelopment at 6 months. Based on the clinical picture of seizures in the context of pertussis infection and investigations excluding other causes, pertussis encephalopathy was diagnosed.
The incidence of pertussis has increased due to waning immunity, with disease presentation being less typical and potentially misdiagnosed. Although 90% of cases occur in developing countries, sporadic outbreaks still occur in countries with high immunisation rates, for example, the current outbreak in England and Wales despite the accelerated primary immunisation schedule.1 ,2 In Australia, epidemics occur every 3–4 years.3
Among vaccine preventable diseases, pertussis causes the greatest morbidity in children in Australia.3 Infants under 6 months old are at the highest risk of complications. Mortality is approximately 1% with the majority of deaths in those younger than 2 months.3
Pertussis encephalopathy is an uncommon but serious complication occurring in 0.5%–1% of all cases, but higher in those under 2 years old.4 The diagnosis is suggested by seizures with pertussis infection in the absence of other diagnoses. Pertussis encephalopathy can present with seizures which can have no neurological consequences or which progress to focal neurology and coma. Although the exact pathophysiology is unclear, proposed mechanisms include central nervous system haemorrhage due to increased venous pressure from coughing paroxysms, hypoxia, vascular occlusions/venous stasis from lymphocytic plugs, hypoglycaemia, exacerbation of unrecognised underlying neurological conditions and effects of toxins produced by B pertussis, although the organism has never been isolated from CSF.4 In a recent case of a child with pertussis encephalopathy there was demyelination on MRI with associated increased myelin protein.5 Our patient had less severe manifestations of pertussis encephalopathy, but his MRI was abnormal which is unusual.
This case highlights a potentially serious complication of pertussis infection and a preventable cause of encephalopathy. It underlines the importance of pertussis immunisation in reducing transmission to infants who are at risk of severe complications such as encephalopathy. In Australia, pertussis booster is recommended in adolescents to boost waning immunity. In addition, due to the current pertussis outbreak, all parents of newborns are funded to receive pertussis immunisation to prevent infant pertussis and its complications. Other strategies include offering pertussis immunisation to pregnant women, as is now occurring in the UK.6
Contributors LKC looked after the patient and drafted and edited the manuscript. DB and JB looked after the patient and edited and provided helpful comments on the manuscript. PAB looked after the patient, provided major editing to the manuscript and is responsible for the overall content.
Competing interests None.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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