|Author||Anonymous (Reviewed by Will Gibson, Alison Leibowitz, and Yazan Daaboul)|
|Exam Type||USMLE Step 1|
|Prompt||A 32-year-old man is brought to the emergency department by his wife for progressive bilateral weakness, loss of sensation, and distal paresthesias in his lower extremities over the past 5 days. The patient can no longer walk and must be carried onto the examination bed. He denies any recent history of trauma. The only illness he can recall is an episode of nausea, vomiting, and bloody diarrhea 3 weeks ago, from which he recovered spontaneously without medications. Neurological examination is remarkable for a motor strength of 1/5 in both lower extremities with loss of deep tendon reflexes. What is the most likely organism responsible for this patient's condition?|
|Answer A||Streptococcus pyogenes|
|Answer A Explanation||[[AnswerAExp::Development of Guillain-Barré syndrome is not commonly associated with Streptococcus pyogenes infection. S. pyogenes infection is associated with development of scarlet fever, rheumatic fever, pharyngitis, and post-infectious glomerulonephritis.]]|
|Answer B||Clostridium species|
|Answer B Explanation||[[AnswerBExp::Clostridium species include:
None of these species is commonly associated with the development of Guillain-Barré syndrome.]]
|Answer C||Staphlococcus aureus|
|Answer C Explanation||[[AnswerCExp::Development of Guillain-Barré syndrome is not commonly associated with Staphylococcus aureus infections. S. aureus is a gram-positive coccus that is a component of the normal skin flora. However, it commonly causes toxin-induced (rapid-onset) food poisoning, cellulitis, and pneumonia. Rarer diseases caused by S. aureus include toxic shock syndrome (TSS), and staphylococcal scalded skin syndrome (SSSS).]]|
|Answer D||Campylobacter species|
|Answer D Explanation||[[AnswerDExp::Campylobacter jejuni is one of the most common infectious organisms that are associated with the development of Guillain-Barré syndrome.]]|
|Answer E||Neisseria meningitidis|
|Answer E Explanation||[[AnswerEExp::Neisseria meningitidis is not commonly associated with the development of Guillain-Barré syndrome. Neisseria meningitidis is an encapsulated, gram-negative diplococcus that typically causes meningitis among unvaccinated sexually active young adults (e.g. college dormitories).]]|
|Explanation||[[Explanation::This patient has symptoms and signs consistent with Guillain-Barré syndrome (GBS). GBS is an autoimmune peripheral neuropathy characterized by an acute areflexic symmetrical ascending flaccid paralysis that usually occurs several weeks following a self-limited upper respiratory tract or abdominal infection. GBS may also affect the cranial nerves in approximately 50% of patients. With the eradication of poliovirus in the developed world, GBS is currently the most common cause of acute flaccid paralysis. It is a type IV hypersensitivity disorder that results in segmental demyelination and secondary axonal degeneration due to infiltration of T-cells and macrophages, complement activation, and antibody formation against Schwann cells by the process of molecular mimicry.
GBS is a neurological emergency, in which the patient must be monitored in an intensive care setting because of its high likelihood of autonomic dysfunction (bradycardia, wide swings in blood pressure, and progression to diaphragmatic paralysis and respiratory failure). Mechanical ventilation is eventually required in up to 30% of patients. Although generally regarded to have a good prognosis, approximately 20% of patients suffer permanent disability, and approximately 5% die despite appropriate therapy. The majority of patients recover spontaneously from the disease. Miller Fisher syndrome is an important variant of GBS; it is characterized by the presence of ophthalmoplegia, ataxia, and areflexia.
Diagnosis of GBS is often suspected by the presence of symptoms and signs and is confirmed by nerve conduction studies. In suspected cases of GBS, a lumbar puncture is typically performed to rule out infectious etiologies of neuropathies. Classically, the lumbar puncture among GBS patients reveals albumino-cytologic dissociation, which is evident in approximately half of patients within the first week of illness. In addition to respiratory support, plasma exchange or immunotherapy by IVIg is often required to hasten recovery. The use of steroids is not effective.
Campylobacter species is the most common infectious organism that is associated with the development of GBS. Campylobacter jejuni is a comma-shaped, gram-negative, oxidase-positive rod that is considered a major cause of infectious bloody diarrhea. It is transmitted by the fecal-oral route. Spoiled poultry, meat, and unpasteurized milk are also common sources of Campylobacter jejuni gastrointestinal infection. Campylobacter jejuni has the ability to grow at 42oC. Other less common infectious agents associated with the development of GBS include CMV, EBV, VZV, and Mycoplasma pneumoniae.
|Keyword||Neurology, Neuropathy, Paralysis, Hypersensitivity, Autoimmune, Mimicry, Schwann, Guillain Barre syndrome, Campylobacter jejuni, Gastroenteritis|
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