Polycystic kidney disease (PKD) is a genetic disorder characterized by the growth of numerous fluid-filled cysts within the kidneys. While often associated with adults, this inherited condition can also affect children. Understanding PKD in children involves its genetic origins and potential challenges. Although PKD can lead to serious health concerns, advancements in medical care offer various approaches to manage the condition and support affected children.
Types and Genetic Basis
Polycystic kidney disease in children has two primary genetic forms: Autosomal Recessive Polycystic Kidney Disease (ARPKD) and Autosomal Dominant Polycystic Kidney Disease (ADPKD). ARPKD is a rarer form, affecting about 1 in 20,000 live births, and is inherited when a child receives two faulty gene copies, one from each parent. Both parents must be carriers of the mutated gene, typically PKHD1, for their child to develop ARPKD. The PKHD1 gene produces fibrocystin, a protein important for kidney tubules and liver bile ducts.
When the PKHD1 gene is mutated, dysfunctional fibrocystin leads to abnormal development of kidney collecting ducts and bile ducts. This abnormality leads to cyst formation, causing kidneys to become enlarged and scarred. The cysts impair kidney waste filtration, and about half of infants with ARPKD may also have an enlarged liver.
ADPKD is a more common genetic condition, affecting about 1 in 400 to 1000 live births. It requires only one mutated gene copy (PKD1 or PKD2) from a single affected parent. A parent with ADPKD has a 50% chance of passing the condition to each child. PKD1 mutations account for about 85% of ADPKD cases; PKD2 mutations are less common.
The PKD1 and PKD2 genes encode polycystin-1 and polycystin-2, proteins that regulate kidney cell function, tubular structure, and fluid secretion. Mutations in these genes lead to dysfunctional proteins, causing cells to behave abnormally and resulting in characteristic cyst growth. While cysts can begin forming in childhood, ADPKD often does not present significant symptoms until adulthood, though early onset and rapid progression can occur in some pediatric patients.
Recognizing Signs and Diagnosis
Recognizing PKD signs in children can be challenging, as symptoms vary by PKD type and age. In newborns and infants with ARPKD, severe manifestations may include an enlarged abdomen due to enlarged kidneys, and respiratory distress. High blood pressure (hypertension) is common, and infants may also experience frequent urination, excessive thirst, and poor growth. Recurrent urinary tract infections (UTIs) are also common.
For children with ADPKD, symptoms often appear later in childhood or even adulthood, but some can present earlier. Common signs in children might include increased frequency of urination, high blood pressure, and pain in the side or back. While many children with ADPKD may not show problematic symptoms, about a quarter might experience issues such as blood in their urine or UTIs.
Diagnosis for PKD in children often begins with imaging. Prenatal ultrasound may detect enlarged kidneys with cysts or reduced amniotic fluid. After birth, a pediatric nephrologist may use postnatal imaging like ultrasound or Magnetic Resonance Imaging (MRI) to confirm renal cysts and assess kidney size and structure. These techniques visualize cyst formation and any associated liver involvement.
Blood tests evaluate kidney function by measuring creatinine and blood urea nitrogen, indicating waste filtration. Urine tests check for protein or blood, and detect urinary tract infections. Genetic testing for PKHD1, PKD1, or PKD2 gene mutations confirms the diagnosis and identifies the specific PKD type, especially helpful without a clear family history or for genetic counseling.
Treatment and Management Approaches
Managing polycystic kidney disease in children focuses on alleviating symptoms, preserving kidney function, and preventing complications. A primary goal is controlling blood pressure, as hypertension is common in children with PKD. Medications like angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) are prescribed to manage high blood pressure and protect kidney function. Regular blood pressure monitoring is standard care.
Pain management is important, particularly if children experience discomfort from enlarged kidneys or cyst infections. This may involve over-the-counter or prescribed pain relievers, selected to avoid further kidney strain. Dietary modifications are also recommended, including a low-sodium diet to help control blood pressure and fluid retention. Adequate hydration is important to prevent kidney stone formation and support overall kidney health.
Preventing and treating urinary tract infections is important, as these can further damage kidney tissue. Children with PKD are monitored for UTIs, and antibiotics are prescribed as needed. Growth support is also considered for children whose kidney disease impacts their development. This might involve nutritional interventions or other therapies to ensure proper growth.
When kidney function significantly declines, more intensive interventions may be necessary. Dialysis (hemodialysis, filtering blood using a machine, or peritoneal dialysis, filtering blood within the body using a catheter and special fluid) can be initiated to perform the functions of failing kidneys. For children who progress to end-stage kidney disease, kidney transplantation offers a long-term solution, replacing the diseased kidneys with a healthy donor kidney. This complex care requires a multidisciplinary team of specialists, including pediatric nephrologists, dietitians, social workers, and surgeons, to provide comprehensive support for the child and family.
Long-Term Outlook and Family Support
The long-term outlook for children with polycystic kidney disease varies based on PKD type and severity at diagnosis. Children with ARPKD, particularly those diagnosed early with severe manifestations, face challenges. About 80% of those surviving the newborn period live into adulthood with ongoing medical care. Many children with ARPKD will eventually require dialysis or a kidney transplant; over half need such interventions by age 20.
Children with ADPKD have a different progression, with most maintaining normal kidney function throughout childhood and not experiencing significant kidney problems until adulthood. Continuous monitoring is important as the disease is progressive, meaning cysts can grow over time and eventually impair kidney function. Regular follow-up appointments with a pediatric nephrologist are standard, occurring every one to two years, to monitor kidney function, blood pressure, and cyst growth.
Families navigating PKD in children can benefit from various support systems. Connecting with patient advocacy organizations and support groups provides opportunities to share experiences, gain insights, and access educational resources. These networks can offer emotional support and practical advice. Psychological support services can help children and their families cope with the emotional impact of living with a chronic illness. Adherence to prescribed care plans and ongoing communication with the medical team are important for optimizing the child’s health and managing the condition.