A 5-month-old boy with no notable medical history presented with weakness, poor feeding, and constipation. His poor feeding had gradually progressed over two weeks: he would tire easily and cough when trying to swallow. He had had constipation for seven to eight days, and had grown progressively weaker, now unable to lift his head off the bed.
His family denies fever, vomiting, focal weakness, and seizure-like activity. Vaccinations are up to date, and his mother said he was born full-term through an uncomplicated vaginal delivery. The family lives on a farm with various livestock.
Find the diagnosis and case discussion on p. 16.
Diagnosis: Infant Botulism
Unlike its better-known brethren, foodborne botulism, which is caused by the ingestion of preformed botulin toxins in tainted foods (e.g., home canning), infant botulism is caused by the ingestion of the entire Clostridium botulinum spore. Most commonly seen between the first and sixth month of life, infant botulism, though rare, can be life-threatening.
The C. botulinum spores colonize the infant's intestinal tract, allowing the toxin to be produced. This potent toxin prevents the release of multiple neurotransmitters, most notably acetylcholine, and the blockage of these cholinergic synapses causes a symmetric, descending motor weakness and flaccid paralysis with autonomic dysfunction. (BMC Microbiol 2010;10:267.)
Infants are at increased risk because studies have shown that the absence of competitive microbial flora enables the growth of the ingested spores. (Clin Microbiol Rev 2006;19:298.) As a result, infants, who have not yet become colonized with normal gut flora, are at high risk of becoming colonized with the botulinum spores. (Clin Microbiol Rev 2006;19:298.) Despite its common association with honey, C. botulinum is actually most often linked to soil and dust exposure. Living in a rural area and with someone who works with soil are risk factors for bacterial colonization. (Pediatr Neurol 2005;32:149.)
The first clinical symptom of infant botulism is constipation. Infants then experience loss of head control (from weakness of the neck muscles), followed by symmetric, descending hypotonia and weakness, ultimately progressing to involve the diaphragmatic muscles. (Annu Rev Med 1980;31:541.) Infant botulism is distinguished from other neurological disorders by the presence of symmetric cranial nerve palsies. These include ptosis, fatigable pupillary response to light, ophthalmoplegia, poor suck, decreased gag reflex, difficulty swallowing, and expressionless facies. (Pediatrics 2007;119:826.)
Diagnosis of infant botulism is achieved via bioassay, and this study unsurprisingly may take many days to return, leaving the treatment team with the dilemma of treating without a conclusive diagnosis. This is complicated even more so because the definitive treatment, intravenous botulism immunoglobulin (BabyBIG), is only available through the California Department of Public Health, so infant botulism remains a clinical diagnosis. Supportive care should pay special attention to airway protection, whether there is a need for mechanical ventilation, positioning to decrease aspiration risks, and urinary retention.
This patient was admitted to the PICU to monitor his airway while awaiting BabyBIG, which was administered the following day. Two weeks later, the immunoassay returned positive for botulism toxin, and he made a full recovery.
Differential Diagnosis for Infant Weakness
- Electrolyte abnormalities
- Botulism metabolic abnormalities
- Muscular dystrophies
- Myasthenia gravis
- Spinal cord trauma
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