Primary Periodic Paralysis (PPP) is a rare condition that causes attacks that affect your muscles, resulting in extreme muscle weakness or temporary paralysis, most often with an inability to stand independently, or even sit up. Primary periodic paralysis is not just one condition, but a group of inherited neuromuscular disorders. Although this condition is very rare, it affects about 5,000 to 6,000 individuals in the US or ~3 in every 200,000 people.