WBR0006

Author	PageAuthor::Anonymous (Reviewed by Will Gibson, Alison Leibowitz, and Yazan Daaboul)
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology
Sub Category	SubCategory::Genitourinary, SubCategory::Neurology
Prompt	[[Prompt::A 32-year-old man is brought to the emergency department by his wife for progressive bilateral weakness, loss of sensation and distal paresthesia in his lower extremities over the past 5 days. The patient can no longer walk and must be carried onto the exam 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	AnswerA::''Streptococcus pyogenes''
Answer A Explanation	[[AnswerAExp::Guillain-Barré syndrome is not commonly associated with Streptococcus pyogenes. S. pyogenes infection is associated with scarlet fever, rheumatic fever, pharyngitis, and post-infectious glomerulonephritis.]]
Answer B	AnswerB::''Clostridium'' species
Answer B Explanation	[[AnswerBExp::Clostridium species include: C. botulinum is associated with flaccid paralysis due to toxin. The paralysis is typically described as symmetrical descending paralysis. C. difficile is associated with pseudomembranous colitis C. tetani is associated with spastic paralysis. Toxin inhibits the release of inhibitory neurotransmitters. None of these species are commonly associated with the development of Guillain-Barré syndrome.]]
Answer C	AnswerC::''Staphlococcus aureus''
Answer C Explanation	[[AnswerCExp::Guillain-Barré syndrome is not commonly associated with Staphylococcus aureus. S. aureus is a gram-positive coccus that is a component of normal skin flora. However, it commonly causes toxin-induced rapid-onset food poisoning, cellulitis, and pneumonia. Rarer conditions caused by S. aureus include toxic shock syndrome, and staphylococcal scalded skin syndrome.]]
Answer D	AnswerD::''Campylobacter'' species
Answer D Explanation	[[AnswerDExp::Campylobacter jejuni is one of the most common infections associated with Guillain-Barré syndrome.]]
Answer E	AnswerE::''Neisseria meningitidis''
Answer E Explanation	[[AnswerEExp::Neisseria meningitidis is not associated with the development of Guillain-Barré syndrome. Neisseria meningitidis is an encapsulated, gram-negative diplococcus that ferments maltose. Neisseria meningitidis typically causes meningitis in unvaccinated sexually active adults.]]
Right Answer	RightAnswer::D
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 after a self-limited upper respiratory tract or abdominal infection. It may also affect cranial nerve-innervated muscles in approximately 50% of patients. It is nowadays considered 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. It is a neurological emergency, in which the patient must be monitored in an intensive care setting because of its high likelihood of autonomic dysfunction, such as bradycardia, wide swings in blood pressure, and pogression to diaphragmatic paralaysis 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. Most 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 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 frequently performed to rule out infectious etiologies of neuropathies. Classically, the lumbar puncture among GBS patients reveals albuminocytologic dissociation that is found in approximately half of patients within the first week of illness. In addition to respiratory support, immunotherapy by plasma exchange or IVIg is required. The use of steroids is not effective. Campylobacter species is one of the most common organisms associated with 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 common sources of Campylobacter jejuni gastrointestinal infection. Campylobacter jejuni is known for its ability to grow at 42oC. Other less common infectious agents associated with GBS include CMV, EBV, VZV, and Mycoplasma pneumoniae Educational Objective: Guillain-Barré syndrome (GBS) is an autoimmune peripheral neuropathy characterized by acute-onset ascending flaccid pralysis and distal paresthesias. It commonly follows a self-limited gastrointestinal infection by Campylobacter jejuni. References: Yuki N, Hartung H. Guillain-Barre syndrome. N Engl J Med. 2012;366:2294-304 First Aid 2014: page 484 First Aid 2013: page 444]]
Approved	Approved::Yes
Keyword	WBRKeyword::Neurology, WBRKeyword::Neuropathy, WBRKeyword::Paralysis, WBRKeyword::Hypersensitivity, WBRKeyword::Autoimmune, WBRKeyword::mimicry, WBRKeyword::Schwann, WBRKeyword::Guillain, WBRKeyword::Barre, WBRKeyword::Syndrome, WBRKeyword::Campylobacter, WBRKeyword::jejuni, WBRKeyword::gastroenteritis, WBRKeyword::bloody, WBRKeyword::diarrhea
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