Paroxysmal extreme pain disorder (Q89738)

Paroxysmal extreme pain disorder is a rare disorder of abnormal pain sensation. This condition presents in the first year of life with episodes of severe rectal pain following bowel movements. This is often accompanied by reflex anoxic seizures (RAS). Finally there is a colour change down one half of the body; either horizontally from the waist down or involving one half of the body as in the harlequin phenomenon.