Almost everyone with ARPKD is diagnosed during infancy or childhood, with about 10% of children diagnosed after 5 years of age. The first signs of the disease vary greatly. Thirty to 50% of ARPKD infants die at birth or shortly thereafter, primarily as a result of underdeveloped lungs and pulmonary complications. This is because lung maturation is dependent on sufficient amniotic fluid being present during fetal lung development. Oligohydramnios (limited or no amniotic fluid) results in hypoplasia (underdevelopment) of the lungs. Besides the potential for poor lung development, neonates (less than 30 days of age) may be premature (less than 37 weeks gestation), have low serum sodium (salt) levels, and water imbalances. Renal function may be compromised during the newborn period, but death caused primarily by renal failure during the neonate period is extremely rare.
Huge cystic kidneys may impair a newborn’s breathing effort or cause delivery complications. The infant may “grow into” and accommodate the massive size of the kidneys. Infants with true lung hypoplasia often die soon after birth from pulmonary insufficiency. At this time technology doesn’t exist to prenatally determine which mechanically ventilated infants will have hypoplasia incompatible with life. Severe respiratory distress can be caused by reversible fluid overload, neonatal lung disease, or limited diaphragm movement from massively enlarged kidneys. In some instances selective nephrectomies have allowed room for lung expansion when severely limited diaphragm movement was due to kidney pressure. Respiratory complications include pneumothoraces, atelectasis, meconium aspiration, bacterial pneumonia, or surfactant deficiency.