Clinical Reasoning: A 2-year-old child with acute flaccid paralysis.

SECTION 1 A 2-year-old boy with a history of autism spectrum disorder and speech delay presented with refusal to walk for a day in late December 2014. In addition to leg weakness, he developed constipation and urinary retention for 2 days. There was no history of pain, altered sensorium, cranial nerve deficits, or upper limb weakness. There was no preceding fever, immunizations, sick contacts, travel, or trauma. Birth and family history was unremarkable. He was fully immunized. On neurologic examination, he was awake and alert without cranial nerve deficits. Muscle tone was normal; he had limited leg movements compared to the upper limbs. Tendon reflexes were diminished at the knees and ankles; plantars were flexor. On sensory examination, he withdrew with tactile stimuli.