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One Pill Can Kill: A Case of Botulism Poisoning
Not every poison is in a pill; in this case of One Pill Can Kill, we’ll explore a toxin that in tiny amounts can be deadly in infants.
You are called to a detached residence at 19:45; it’s the first call of your night shift, but it won’t be your last. You arrive at an open door and are led to the kitchen, where two parents are dotting over a five-month-old girl sitting in a high chair. Sitting might not be the right word; she looks exhausted, her head flopped forward and mashed peas dripping from her chin to her bib. “For three days now, she hasn’t been eating as much as usual, and today she’s not eating anything at all. She’s just sleeping all the time!” the parents describe, walking over each other's anxious words.
Something in your brain can’t reconcile what you are seeing; she isn’t pale or cyanosed or toxic looking. Through slits, you can barely make out her eyes, but she isn’t unconscious; her work of breathing isn’t distressed. But some things are not right. You finally put your finger on the problem: she’s floppy. As you unclip her safety strap, you pick her up and realize she’s got almost no tone; by this age, she should be able to hold her head up, but she makes no effort to do so; you place her on her back and tickle her feet, expecting her little legs to kick or tug backward, but she barely flexes her knees.
A full set of vitals isn’t concerning; for her age, heart rate, respiratory rate, SpO2, and temperature are all normal, and her cap refill is less than two seconds. You contemplate searching for a tiny blood pressure cuff but decide in the absence of signs of poor perfusion, you won’t bother.
You take a quick history; the child had a normal birth, has hit her developmental milestones, and her three siblings, aged 2 years to 7 years, have no medical problems. Perplexed, you grasp at oddball questions, not knowing where you’re leading with this, but hoping something comes up.
Are there any medications lying around? No.
Has there been any travel? No.
Does she visit a daycare or nursery where she might have picked up a virus? No.
Any new pets? Nope. New creams? No. New foods? No.
You must be missing something. You remember your preceptor, way back when, emphasizing the physical exam: “If you don’t know what’s going on, you haven’t examined your patient thoroughly.”
You return to the basics:
There are no focal deficits, and pupils are equal; it doesn’t appear to be a stroke or brain bleed.
There is no bruising or tenderness; it doesn’t appear to be traumatic.
The face and neck seem weaker than the arms and legs; this is called a descending pattern.
Exasperated at the medical mystery, you decide to package the baby up in a car seat and secure her to the stretcher for the trip to the pediatric hospital 25 minutes away. You don’t have much of a therapeutic plan, other than to watch her like a hawk; something is definitely wrong.
Time Out: What’s your differential diagnosis for this weak infant?
Back to the case:
Your barrage of questions has triggered a memory: the mother tells you that, four nights ago, a babysitter – reliable and mature – was caring for the kids while they went out to a fundraiser. She places a quick phone call and checks if anything unusual occurred; it’s revealed that the babysitter, distraught over her inability to soothe the crying infant, took to TikTok for a soothing solution. She saw that babies have a sweet tooth; she gave the baby honey that she found in the fridge.
A biological neurotoxin
It’s absolutely true that babies stop crying when given something sweet; in the ER, we use sucrose syrup to sedate babies needing a lumbar puncture, for example. But honey is famous for carrying spores of Clostridium botulinum, bacteria that produce the neurotoxin that causes botulism. Botulinum poison affects motor end plates – the distal part of motor nerves that release the neurotransmitter acetylcholine. Acetylcholine crosses the synapse to trigger muscle contraction; if it’s not released, muscles are flaccid.
The textbook presentation of weakness is a bilateral, symmetrical, descending hypotonia (weakness or paralysis). Symptoms can range from mild to severe. The first sign in infants is often constipation as the bowels slow; lethargy, poor feeding, difficulty swallowing, and loss of head control follow. In severe cases, respiratory muscles weaken and death can be due to respiratory failure. A common giveaway in babies is ptosis or droopy eyelids. Adults may describe diplopia as extraocular muscle weakness, speech difficulties, and dry mouth.
In the hospital, stool samples are sent to detect the toxin. Treatment is antitoxin, an immunoglobulin that reverses symptoms.
Other diseases have overlapping presentations with botulism; myasthenia gravis, Guillain-Barré syndrome, tick paralysis, and organophosphate poisoning can all affect neuromuscular junctions.
Babies are particularly susceptible because their gut microbiome is immature. It’s not just babysitters that might err and give honey to babies; many cultures have widespread practices of giving babies pre-lactal feeds that may contain honey. Further, a wellness fad has shifted diets towards “natural” foods with refined sugar getting shunned and replaced with honey. And clostridium spores aren’t only in honey; spores can be found in the environment, including soil and dust; it can be inhaled or infect wounds and have even been unintentionally mixed into recreational heroin and injected. Iatrogenic poisoning can occur from Botox injections. Lastly, some countries have purified botulinum toxin for use as an aerosolized bioweapon.
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