Background

Infantile botulism is rare in the UK. Only 10 cases have been reported between 1976 and 2009; all of which have required admission to hospital. Approximately 90% of cases worldwide occur in those younger than 6 months old.

This case highlights the diagnostic challenge of infantile botulism. In the absence of classical electromyographic findings, a diagnosis of botulism was not considered likely and the infant was thought to have neurodegenerative process that would quickly lead to death. Only when the electromyogram (EMG) was repeated showing a different pattern was a stool sample sent and withdrawal of care measures postponed. The therapeutic window for treatment had long passed by the time a diagnosis was reached.

Clinicians must consider infantile botulism in the differential diagnosis of weakness in infancy and send an appropriate stool sample for PCR early in the clinical course. Diagnosis may be very difficult, particularly if EMG studies are not classical, and treatment should be started as early as possible if botulism is clinically suspected.

Labelling of honey jars was first implemented in 1996; however, there continues to be a need for greater public awareness of the harmful effects of honey to infants less than 1 year.

Case presentation

A term, previously well, male infant presented to his hospital aged 2 months with a 6-day history of poor feeding, constipation and irritability. He was less interactive with poor fixing and following. He was dehydrated on examination and had fluid resuscitation and antibiotics for presumed sepsis.

He was a thriving, breastfed infant with a regular bowel pattern. Of note, there was a background social history of maternal heroin use in the first trimester and ongoing methadone dependency.

He was transferred to the regional tertiary neurology centre for investigation of generalised weakness. He was found to be globally hypotonic with poor head control and spontaneous but weak movement of all four limbs. There were upper but no lower limb reflexes. He had a poor suck, no rooting reflex and reduced gag reflex. He had no cry though vocalised weakly. Funduscopy revealed no papilloedema or retinal haemorrhages. Pupils were equal and reactive but he was unable to fix or follow.

He was started on gentamicin, cefotaxime, aciclovir and dexamethasone for a presumed diagnosis of encephalopathy. These were discontinued following negative cerebrospinal fluid and blood cultures. Nasopharyngeal secretions were positive for rhinovirus and a chest x-ray (CXR) showed mild right-middle lobe opacification. Investigations for his neurological pathology are detailed in table 1. He became pale and hypotonic a few days later necessitating admission to the high dependency unit. His CXR revealed ongoing right-middle zone changes and he was started on co-amoxiclav and continuous positive airway pressure (CPAP). He continued intermittently on CPAP for a number of days and appeared to show signs of improvement.

On day 16 of admission he had abnormal movements in keeping with a generalised tonic-clonic seizure and was treated with midazolam and phenytoin. His electroencephalography was entirely normal. A tensilon test was performed, which was also normal, and an EMG suggested central rather than peripheral weakness.

He was admitted to the paediatric intensive care unit (PICU) on day 32 following a profound apnoea and desaturation requiring intubation and ventilation. Given the deteriorating nature of his condition and negative investigations at that time, he was thought to have a neurodegenerative condition with a poor prognosis. End-of-life care was discussed with parents and arrangements made for baptism.

In attempts to reach a definitive diagnosis, a MRI scan was repeated and was again normal. Neurophysiology was repeated and revealed a changing pattern in keeping with a peripheral myopathic process. Therefore infantile botulism could not be excluded and a stool sample was sent to the national reference laboratory. On day 41 of admission, Clostridium botulinum type A was isolated by PCR on his stool sample. The diagnosis of infantile botulism was made and public health authorities informed. History from both parents revealed the infant had been getting honey on his soother at home. A sample of the honey from the jar used subsequently tested positive for C botulinum type A. Given the duration of symptoms prior to diagnosis, the decision was made not to administer immunoglobulin.

Seven weeks after initial presentation the infant failed a trial of extubation and showed no signs of sustained neurological improvement having initially recovered some power in his limbs. A tracheostomy was performed and he remained dependant on CPAP ventilation 3 months after presentation. He continued to secrete C botulinum in stool samples tested weekly.

Differential diagnosis

Neurodegenerative process of uncertain aetiology.

Treatment

Treatment with human-derived botulinum anti-toxin (Baby BIG-IV) has been available in the USA since 2003 and was used in similar cases in the UK in 2007 and 2009. It is associated with fewer side effects, such as serum sickness, than traditionally used ovine derived anti-toxin. Current recommendations suggest not treating if symptom onset is greater than 10 days before diagnosis, as in this case. Treatment should be started if botulism is suspected without waiting for laboratory confirmation.

Outcome and follow-up

At the time of writing, the infant had been discharged home after successfully weaning off all respiratory support. He was assumed to have made a full recovery but will be followed up in the out-patient clinic as a matter of routine.