Guillain-Barré Syndrome
The most likely diagnosis is D. Guillain-Barré syndrome (GBS), based on the classic triad of ascending weakness, areflexia, and preceding upper respiratory tract infection. 1
Clinical Reasoning
This patient presents with the pathognomonic features of GBS:
- Ascending pattern of weakness: Started in lower limbs and progressed upward to upper limbs, which is the classic presentation of GBS 1, 2
- Areflexia: Total absence of reflexes in all limbs is a cardinal feature, present in almost all patients at nadir 1, 2
- Sensory involvement: Tingling sensation (paresthesias) and moderate sensory symptoms are common in GBS, though not required for diagnosis 2, 3
- Preceding infection: Upper respiratory tract infection weeks before onset is typical, as GBS is triggered by infections in approximately two-thirds of cases 1, 4
- Acute onset with rapid progression: Two-day history fits the acute-to-subacute timeframe, as most patients reach maximum disability within 2 weeks 1
- Pain preceding weakness: Muscle pain is frequently reported and can be muscular, radicular, or neuropathic in nature 1, 5
Why Other Diagnoses Are Less Likely
Viral myelitis (Option A) would typically present with:
- Upper motor neuron signs (hyperreflexia, positive Babinski sign) rather than areflexia 6
- Sensory level on examination 6
- Bladder/bowel dysfunction early in the course 6
Epidural abscess (Option B) would show:
- Severe localized back pain as the predominant feature 6
- Fever and systemic signs of infection 6
- Rapid progression over hours to days, not the ascending pattern described 6
Transverse myelitis (Option C) would demonstrate:
- Clear sensory level on the trunk 6
- Upper motor neuron signs with hyperreflexia below the lesion 6
- Early sphincter dysfunction 6
Critical Diagnostic Pitfalls
Common mistake: Dismissing GBS because reflexes can occasionally be normal or even exaggerated in the pure motor variant with AMAN subtype, but this patient has total areflexia which is classic 1
Important caveat: If progression continues beyond 4 weeks from onset, consider acute-onset chronic inflammatory demyelinating polyradiculoneuropathy (A-CIDP), which occurs in approximately 5% of patients initially diagnosed with GBS 7, 5
Immediate Next Steps
This patient requires urgent evaluation given the potential for rapid deterioration:
- Neurologic consultation immediately 1, 2
- Respiratory function monitoring using the "20/30/40 rule": vital capacity <20 mL/kg, maximum inspiratory pressure <30 cmH₂O, or maximum expiratory pressure <40 cmH₂O indicates risk of respiratory failure 2
- MRI of spine with or without contrast to rule out compressive lesions 1, 2
- Lumbar puncture: Expect elevated protein with normal or mildly elevated white blood cells (albuminocytologic dissociation) 1, 2
- Electrodiagnostic studies to confirm peripheral nerve dysfunction and distinguish between AIDP, AMAN, and AMSAN subtypes 1, 7
- Admission to unit with ICU capability given 20% of GBS patients develop respiratory failure requiring mechanical ventilation 1