Case Study: An 8-Week-Old Infant with Weak Cry, Hypotonia, and Respiratory Distress

Answer

C. Infant botulism

Why?

• Infant botulism typically presents between 2–26 weeks with constipation, poor feeding, weak cry, hypotonia, bulbar palsy, and respiratory distress.

• In this case, the infant had constipation, a weak cry, ptosis, hypotonia, and autonomic instability — a classic constellation of findings.

• History revealed honey ingestion, a recognized risk factor.

• PCR of stool confirmed Clostridium botulinum.

Why not the others?

• SMA: Progressive hypotonia and tongue fasciculations, but not acute onset with autonomic instability.

• Guillain–Barré syndrome is very rare in this age group; reflexes are usually absent rather than just diminished, and the disease course is not typically this acute.

• Viral encephalitis: Would present with fever, seizures, altered consciousness, abnormal neuroimaging, or CSF—not seen here.

Introduction

Botulism in infants is a rare, life-threatening disorder of the neuromuscular junction characterized by the germination of Clostridium botulinum spores in the immature intestine, which produces a neurotoxin. It usually affects infants under six months of age, presenting with constipation, feeding difficulties, a weak cry, hypotonia, and progressing respiratory failure. The following highlights the diagnostic challenge and clinical course leading to a positive diagnosis of infant botulism in an eight-week-old, emphasizing the importance of early symptom recognition and treatment.

Case Presentation

Initial Presentation

An 8-week-old boy was brought to the emergency department (ED) with inconsolable crying, lethargy, weakness, and hypoxemia.

• History of present illness: The infant was previously healthy until 7 days prior, when he became irritable, followed by prolonged crying spells. One day before ED arrival, his crying became continuous, and his condition worsened. The grandmother reported that palpation of the right abdomen aggravated his crying.

He had been evaluated previously at another facility, where examination and vital signs were normal, and he was discharged with a diagnosis of abdominal colic.

At home, the crying persisted throughout waking hours, with a progressively weaker cry. Feeding deteriorated with a poor latch and weak suck. Limb movements diminished, and he appeared hypotonic. On the final day before admission, he refused breastfeeding entirely, and his mother expressed milk and fed him with a spoon and cup.

Past Medical and Family History

• Gestation & birth: Born at 39 weeks via spontaneous vaginal delivery, no complications.

• Birth weight: 4.5 kg; head circumference normal.

• Development: Appropriate until current illness.

• Immunizations: Not initiated.

• Medications: Vitamin D supplementation.

• Allergies: None known.

• Social history: Lives in a rural household with parents, grandmother, and sibling.

• Maternal history: Depression, anxiety, anemia.

Examination in ED

• Vital signs: Temp 37.2 °C (axillary), HR 153/min, BP 176 mmHg, RR 33/min, SpO₂ 97% on room air.

• Anthropometrics: Weight 7.1 kg, normal growth parameters.

• General: Alert but irritable, weak cry, inconsolable.

• HEENT: Anterior fontanelle open, soft, flat. Pupils round and reactive. Mucous membranes moist.

• Cardiorespiratory: Tachycardia with regular rhythm; lungs clear.

• Abdomen: Soft, no hepatosplenomegaly.

• Skin/Genitourinary: No rash; testes normal.

• Neurologic: Weak cry, decreased spontaneous limb movement, generalized hypotonia, diminished but present reflexes, symmetric face with minimal movement.

Laboratory and Imaging

• CBC: Normal except platelets 621,000/µL.

• CMP: Glucose, lactate, lipase, AST/ALT, bilirubin, BUN/Cr all normal.

• UA & urine toxicology: Negative.

• Respiratory PCR panel (COVID-19, influenza, RSV): Negative.

• Chest X-ray & abdominal ultrasound: Normal.

• MRI brain: Normal.

• Lumbar puncture: Glucose 54 mg/dL, protein 104 mg/dL (mildly elevated), RBC 1055/µL, WBC 2 (lymphocytes).

Empiric therapy with ceftriaxone, vancomycin, and acyclovir was initiated.

Clinical Course in PICU

Six hours later, SpO₂ dropped to 85%, improving with 2 L/min oxygen via nasal cannula. He was admitted to the PICU.

• Respiratory distress: Difficult to arouse, grunting, head bobbing, intercostal retractions, exaggerated abdominal breathing.

• Airway signs: Weak hypophonic cry, inspiratory stridor, copious secretions.

• Neurologic findings: Bilateral ptosis, weak facial movements, minimal spontaneous limb movement, generalized hypotonia, diminished but present reflexes.

• Autonomic instability: Persistent tachycardia and hypertension despite sedation with midazolam, opioids, and benzodiazepines.

He was intubated and mechanically ventilated.

Differential Diagnosis

The team systematically considered causes of irritability, hypotonia, and autonomic instability:

• Infectious: Sepsis, meningitis, pneumonia, UTI → ruled out (normal labs, CSF, imaging).

• Neurologic (CNS): Stroke, hydrocephalus, intracranial mass → unlikely (normal imaging, flat fontanelle, no seizures).

• GI/Urinary: No evidence of intussusception, obstruction, or torsion.

• Oncologic/Metabolic: Leukemia and neuroblastoma, as well as metabolic disorders, were considered unlikely because of normal labs and imaging and the absence of supportive clinical features.

• Neuromuscular: SMA, Guillain–Barré considered but inconsistent (reflexes present, rapid onset).

• Neuromuscular junction: Myasthenia gravis and Lambert-Eaton syndrome are incredibly rare in infants. The collection of constipation, bulbar palsy, weak cry, hypotonia, and autonomic instability made infant botulism the most likely diagnosis.

Key History

Further questioning revealed that the infant had constipation for 2–3 days prior to symptom onset. To treat this, the family had given him honey.

Diagnosis

PCR testing of stool confirmed Clostridium botulinum.
Final Diagnosis: Infant Botulism.

Management of this case

• Specific therapy: BabyBIG® (botulism immune globulin).

• Airway: Intubated for 10 days.

• Recovery signs: Regained ability to move arms against gravity, open eyes, and cough.

• Extubation: Successfully extubated after demonstrating adequate tidal volume and airway protection; transitioned briefly to noninvasive ventilation.

• Feeding: NG tube required for persistent hypotonia and feeding difficulty.

• Rehabilitation: ~10 days, after which feeding and muscle tone improved steadily.

Outcome

At the 3-month follow-up, all symptoms had resolved. The infant was thriving with normal development.

Discussion

This case demonstrates the classic features of infant botulism:

• Early signs: Constipation, irritability, weak cry, poor feeding.

• Neurologic progression: Hypotonia, ptosis, bulbar palsy.

• Respiratory involvement: Progressive weakness requiring mechanical ventilation.

• Autonomic dysregulation: Tachycardia and hypertension despite sedation.

The differential diagnosis of hypotonia in infancy is broad (CNS disorders, SMA, Guillain–Barré, metabolic myopathies, intoxications). However, the combination of constipation, bulbar palsy, weak cry, and autonomic instability is strongly supportive of botulism.

Infant botulism most commonly occurs between 2 and 26 weeks of age. While honey is a known risk factor, many cases result from environmental spore exposure (e.g., soil, dust). In this case, ingestion of honey was the precipitating factor.

Pathophysiology:

Botulinum neurotoxin blocks presynaptic release of acetylcholine at cholinergic neurons, resulting in flaccid paralysis and autonomic dysfunction. In order for infants to recover, they must regenerate new synaptic terminals, which could take weeks.

Management:

The only specific treatment, BabyBIG® (big or human-derived botulism immune globulin), significantly shortens the length of stay in the hospital and complications. Supportive intensive care support, particularly airway and respiratory support, is vital until recovery occurs.

Conclusion

This case highlights that infant botulism should always be considered in the differential diagnosis for infants presenting with constipation, irritability, hypotonia, and respiratory distress. Early recognition, initiation of BabyBIG treatment, and supportive critical care might result in complete recovery.