This anomaly, also called mu-coviscidosis, is the most common of all autosomal recessive disorders. It is usually a generalized defect affecting all the exocrine glands of the body. Pancreas is one of chief sites affected by this disorder. Decrease in fluid and salt secretion by the pancreatic acini results in the production of very thick secretion due to which the duct system is blocked. Dilatation of some parts of the ducts leads to cyst formation. The pancreas is usually small in size and there is a severe deficiency of pancreatic exocrine secretion which can lead to meconium ileus (described later).