Guillain Barr Syndrome

The immune system's friendly-fire demolition

Imagine a city's defense force (immune system) is trained to spot and destroy invaders (germs). After fighting off an invader that has similar-looking armor to the city's own power cables (molecular mimicry: germs and myelin both have gangliosides), the defense force gets confused and starts tearing down the insulation on those power cables (the myelin wrap). The longest cables running to the outer neighborhoods (longest peripheral nerves to the feet) get hit hardest first, so the power dies in the feet first and spreads upward. The city's critical systems—the emergency generators (diaphragm and intercostal muscles) and the heart's rhythm controller (autonomic nerves)—are still standing but getting weaker. Eventually the damage stops spreading (immune attack subsides), repair crews move in (remyelination), and power slowly returns—though some neighborhoods stay dim longer than others.