P PIDD X 200

y More than 200 primary immune deficiency disorders (PIDDs) are recognized. y PIDDs affect 1 in 2,000 children in the United States and 1 in 1,200 children worldwide. y More than 60% of PIDDs are diagnosed in childhood. y Many PIDDs are caused by X-linked recessive disorders: They are ≤4 times more common in boys <16 years of age. y PIDDs are detected in 16% of non–cystic fibrosis bronchiectasis cases in children.