Up to 3% of persons infected with Shigella may later develop a syndrome that includes joint pain and swelling, irritation of the eyes, and sometimes painful urination. This is a reaction to the previous gastroenteritis and is called ìreactive arthritisî or Reiterís Syndrome. Basically, the immune system, intending to fight Shigella, attacks the bodyís cells. Reiterís Syndrome is most common in persons with the human leukocyte antigen (HLA) B27 genetic makeup. Reiterís Syndrome can last for months or years, can lead to chronic arthritis, and may be difficult to treat.