A 32-year-old man is brought to the emergency department due to weakness and tingling that started in his feet and is now at his knees. A week ago, the patient noticed that his legs felt weak while climbing stairs. Since then, the weakness has progressively worsened every day. Today, he fell twice when attempting to walk. Medical history is insignificant, except for a mild respiratory infection 2 weeks ago that resolved spontaneously. The patient does not use tobacco, alcohol, or illicit drugs. He takes no medications. Vital signs are within normal limits. Physical examination shows marked weakness in the distal muscles and moderate weakness in the proximal muscles in both legs. Deep tendon reflexes are absent at the knees. This patient's condition is most likely associated with which of the following?

Question

A 32-year-old man is brought to the emergency department due to weakness and tingling that started in his feet and is now at his knees.  A week ago, the patient noticed that his legs felt weak while climbing stairs.  Since then, the weakness has progressively worsened every day.  Today, he fell twice when attempting to walk.  Medical history is insignificant, except for a mild respiratory infection 2 weeks ago that resolved spontaneously.  The patient does not use tobacco, alcohol, or illicit drugs.  He takes no medications.  Vital signs are within normal limits.  Physical examination shows marked weakness in the distal muscles and moderate weakness in the proximal muscles in both legs.  Deep tendon reflexes are absent at the knees.  This patient's condition is most likely associated with which of the following?

Quizplus · Accepted Answer

11ec160b_39c0_cadb_9249_39ab95a6e113_MD0001_00 This patient has ascending symmetric weakness following a febrile illness, likely due to Guillain-Barré syndrome (GBS). GBS is an acute, immune-mediated, demyelinating polyneuropathy thought to be due to molecular mimicry; infectious antigens provoke an immune response that cross-reacts with the myelin of the spinal roots and peripheral nerves, resulting in demyelination of peripheral nerves. Patients develop a symmetric, ascending flaccid paralysis and areflexia leading to eventual respiratory failure; cranial nerve involvement can also occur. This is typically preceded by an upper respiratory viral illness or an episode of diarrhea (due to Campylobacter jejuni). Histology demonstrates an inflammatory infiltrate located within the endoneurium (the innermost layer of connective tissue that surrounds a nerve axon and its corresponding blood vessel). The infiltrate, consisting largely of lymphocytes and macrophages, extends from the small vessels (perivenular) to the associated nerve axon. Macrophages strip the myelin sheath from the axon, and lipid laden macrophages are seen following the engulfment of myelin. (Choice A) Endomysial inflammatory infiltration is characteristic of polymyositis (an immune-mediated inflammatory myopathy). Patients develop symmetric weakness; however, weakness is greater proximally than distally. (Choice B) Hyalinization of the nerve arterioles leads to ischemic nerve injury and is a cause of diabetic neuropathy. However, this occurs over an extended time (decades) in patients with long-standing, uncontrolled diabetes. (Choice D) Mutations in the gene that codes for the muscle protein dystrophin can cause either a complete absence of this protein (Duchenne muscular dystrophy) or its decreased synthesis (Becker muscular dystrophy). Both of these diseases cause progressive weakness and lead to eventual respiratory failure but weakness is worse proximally and patients present in early childhood with a waddling gait and calf enlargement. (Choice E) Corynebacterium diphtheriae can cause neuropathies due to Diphtheria toxin penetration through the blood-nerve barrier; however, diphtheria usually presents as pharyngitis with pseudomembrane formation and stridor. In addition, the neuropathy typically affects the cranial nerves prior to the peripheral nerves. Educational objective: Guillain-Barré syndrome is an acute demyelinating polyneuropathy. It is thought to be due to molecular mimicry and is commonly preceded by an upper respiratory viral illness or gastroenteritis. Segmental demyelination of the peripheral nerves and an endoneural inflammatory infiltrate are seen on light microscopy.

A 32-Year-Old Man Is Brought to the Emergency Department Due