A 6-month-old boy is brought to the emergency department for lethargy and poor feeding. For the past 4 days, the infant has been sleepier than normal and eating less. His normal daily intake includes 26 oz of formula and a combination of fruit, cereal, honey, and yogurt; however, he has consumed only 10 oz of formula daily in recent days. This morning, when his mother lifted him from his crib, "he was completely floppy." The patient has had no vomiting, fever, abnormal movements, or known trauma. He has had frequent wet diapers daily but has not stooled for a week. Until this past week, the patient was able to sit unsupported and reach for toys. His prenatal course and delivery were uncomplicated, and he takes no daily medications. Immunizations are up to date. Weight and length are at the 25th percentile. Temperature is 36.7 C (98.1 F), pulse is 108/min, and respirations are 36/min. Examination reveals a severely hypotonic and lethargic infant who cries faintly while lying on the examination table. Which of the following additional findings would most likely be seen on physical examination of this patient?

Question

A 6-month-old boy is brought to the emergency department for lethargy and poor feeding.  For the past 4 days, the infant has been sleepier than normal and eating less.  His normal daily intake includes 26 oz of formula and a combination of fruit, cereal, honey, and yogurt; however, he has consumed only 10 oz of formula daily in recent days.  This morning, when his mother lifted him from his crib, "he was completely floppy."  The patient has had no vomiting, fever, abnormal movements, or known trauma.  He has had frequent wet diapers daily but has not stooled for a week.  Until this past week, the patient was able to sit unsupported and reach for toys.  His prenatal course and delivery were uncomplicated, and he takes no daily medications.  Immunizations are up to date.  Weight and length are at the 25th percentile.  Temperature is 36.7 C (98.1 F), pulse is 108/min, and respirations are 36/min.  Examination reveals a severely hypotonic and lethargic infant who cries faintly while lying on the examination table.  Which of the following additional findings would most likely be seen on physical examination of this patient?

Quizplus · Accepted Answer

11ec25c8_d704_68d9_bc81_f9c63de710bd_MD0003_00 Infant botulism is a neurologic condition occurring in children age <1 often following ingestion of honey contaminated with Clostridium botulinum spores. Whereas ingestion of preformed botulinum toxin results in foodborne botulism, infant botulism is caused by intestinal colonization of C botulinum spores that produce the toxin in situ. Infants are particularly vulnerable due to an immature digestive system lacking protective microbiota. C botulinum neurotoxin inhibits presynaptic acetylcholine release into the neuromuscular junction (NMJ), affecting the somatic nervous system (eg, skeletal muscles) and the autonomic nervous system (eg, smooth muscles). Autonomic signaling is impaired first, and constipation from hypoactive bowel, along with poor feeding and irritability, is often the earliest sign of disease (Choice D). Muscles innervated by cranial nerves are typically affected, causing oculobulbar weakness; absent gag reflex, ptosis, ophthalmoplegia, and impaired pupil constriction are common (Choice C). Muscular weakness may progress to a descending paralysis and respiratory failure. Symmetric findings of diminished or absent deep tendon reflexes, decreased strength, and hypotonia are present on examination, but sensory function remains intact (Choice A). Infant botulism is diagnosed by identifying C botulinum spores or toxin in stool. Treatment is intravenous botulism immunoglobulin and supportive care. (Choices B and G) Whereas botulism is a disorder of the neuromuscular junction, a bulging fontanelle and sustained ankle clonus indicate pathology of the central nervous system. This pathology is characterized by upper motor neuron findings such as hypertonia rather than the hypotonia seen in this patient. (Choice E) Muscle fasciculations are seen in organophosphate poisoning due to increased acetylcholine in the NMJ. However, twitching is not typical in botulism as acetylcholine release into the NMJ is reduced. Educational objective: Infant botulism occurs in children age <1 after exposure (eg, ingestion of honey) to Clostridium botulinum spores. Impaired acetylcholine release into the neuromuscular junction causes constipation, irritability, oculobulbar weakness (eg, absent gag reflex, ptosis), hyporeflexia, progressive hypotonia, and eventual paralysis. References: Infant botulism: review and clinical update. (http://www.ncbi.nlm.nih.gov/pubmed/25882077)

A 6-Month-Old Boy Is Brought to the Emergency Department for Lethargy