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Juvenile Nephronophthisis - Symptoms, Causes, Diagnosis, and Treatment

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Juvenile nephronophthisis is fibrosis and inflammation of the kidneys leading to end-stage renal disease in children. Read the article to know more about it.

Medically reviewed by

Dr. Manzoor Ahmad Parry

Published At September 23, 2022
Reviewed AtMarch 13, 2023

What Is Nephronophthisis (NPH)?

Nephronophthisis is a genetically inherited disorder affecting the kidneys. The disorder is inherited as an autosomal recessive trait, the most common cause of kidney failure in children. It is a type of medullary cystic kidney disease. The disorder is characterized by the reduced ability of the renal tubules to concentrate the urine, chronic tubulointerstitial nephritis (cause of acute kidney injury), cystic renal disease (a condition of fluid-filled sacs in the kidney), and end-stage renal disease (permanent damage of the kidneys leading to kidney failure). The disorder leads to kidney failure before the age of 30 years. At the time of conception of an affected individual, there are 25% chances of the offspring being affected by the disorder, 50% of chances being an asymptomatic carrier, and 25% being an unaffected individual without being a carrier. Nephronophthisis (NPH) is of three types-

  • Type1 NPHP1- Juvenile Nephronophthisis: It is the most common type of disorder which occurs from the changes in the NPHP1 gene. The disorder develops into end-stage renal disease at an average age of four to six years. The symptoms are polydipsia, polyuria, growth retardation, fatigue, and chronic iron-resistant anemia. Renal cysts can be found in 50% of the affected individuals.

  • Type2 NPHP2 - Infantile Nephronophthisis: The disorder develops into end-stage renal disease at the age of 13 years. The disorder is characterized by early-onset that can start before work or in early infancy. Nephronophthisis leads to chronic end-stage renal disease within the first five years of life. The size of the kidneys is typically enlarged. The patient suffers from hypertension.

  • Type 3 NPHP3- Adult NPH: This disorder occurring in adults is similar to juvenile NPH, and the end-stage kidney disease develops at the age of 19 years.

What Is Juvenile Nephronophthisis?

Juvenile nephronophthisis is an autosomal recessive disorder caused due to the impairment of the gene NPHP1. This gene is associated with protein synthesis for the tubular interstitial cells. The disorder develops into end-stage kidney disease at the average age of four to six years. Renal insufficiency is present at the time of diagnosis. The kidney size may be small or regular. Typical tubular basement membrane changes with medullary cysts can be seen.

Juvenile nephronophthisis is the most commonly found disorder of the three variants. The patient can have symptoms like tubular dysfunction and a decrease in the ability of the tubules to concentrate the urine. Hypertension is not seen in this type of nephronophthisis. Fluid deprivation with low urine osmolarity is seen in the children, which does not increase with the administration of Desmopressin.

What Are the Symptoms of Juvenile Nephronophthisis?

Early symptoms are caused due to the inflammation and fibrosis of the kidneys leading to impairment. The symptoms include-

  • Polydipsia - Increase in thirst.

  • Polyuria - Increase in the frequency of urination. Polyuria and polydipsia are caused due to decreased urine concentrating ability and the loss of sodium conservation in the kidneys.

  • Growth Retardation - It is due to the decrease in the growth hormones, which causes general growth retardation.

  • General Weakness - It might be due to the body's loss of sodium ions and fluid.

  • Extreme Tiredness or Fatigue - It can be experienced due to dehydration and hyponatremia.

  • Normal Glomerular Filtration Rate - The glomerular filtration rate of the kidneys is not affected in juvenile nephronophthisis.

  • Low Urinary Osmolarity - It is due to decreased concentration defect of the kidney, which does not increase even after the administration of Desmopressin.

  • Hyponatremia - Decrease in the level of sodium in the blood.

  • Hypovolaemia - Excess loss of fluid in the body leads to hypovolemia.

  • Urinary Sodium Wasting - Itis responsible for hyponatremia and hypovolaemia.

  • Chronic Dehydration and Renal Insufficiency - Both can later lead to growth retardation.

  • Absence of Hematuria - Absence of blood in the urine.

  • Blood Pressure - It is normal in patients with juvenile nephronophthisis.

Advanced stages include the symptoms like-

  • Progressive renal insufficiency.

  • Anemia.

  • Metabolic acidosis.

  • Nausea.

  • Anorexia (an eating disorder that occurs in people with low body weight).

  • Weakness.

  • The end-stage renal disease can develop at an average age of 13 years or much later during adulthood.

How to Diagnose Juvenile Nephronophthisis?

Clinical Features - Nephronophthisis can be clinically characterized by the decreased renal capacity to concentrate the urine, cystic renal disease, chronic tubulointerstitial nephritis, and the disease resulting in end-stage renal disease at an average age of 13 years. Based on the age clinically, nephronophthisis can be divided as-.

  • Infantile NPH - Renal manifestations can progress and lead to renal failure before the age of three years.

  • Juvenile NPH - Develop at a certain median age of 13 years. It can be clinically characterized by polydipsia, polyuria, and growth retardation.

  • Adolescent NPH - It is clinically similar to juvenile NPH, and the rate of progression of the disease is up to an average age of 19 years.

Blood and Urine Samples - These can be used to detect the presence of low urine osmolality, hyponatremia, anemia, and hypovolemia. The rest of the changes that are seen in renal insufficiency can be noticed like metabolic acidosis, anorexia, weakness, hematuria, proteinuria, and low creatinine level in urine.

Kidney Ultrasound - On kidney ultrasound in juvenile nephronophthisis, findings such as increased echogenicity, renal cyst in 50% of the affected individuals, and reduced corticomedullary differentiation can be seen.

Histologic Studies - Histology studies can reveal tubulointerstitial scarring, taken and disrupted tubular basement membrane, and cortico medullary cyst with reduced or normal kidney size. Diagnosis of the NPH relies mainly on the presence of characteristic clinical features, kidney ultrasound results, and the genetic identification of variation or deletion in the NPHP1 gene.

How to Manage Juvenile Nephronophthisis?

  • The management of the NPH depends mainly on treating the NPH gene and does not include treating other findings observed in the syndrome.

  • Treatment can include correction of hypovolaemia which is decreased in the water and electrolyte balance, anemia which is reduced in the circulating RBCs (red blood cells), hypertension, if found, protein urea is present, and growth hormone treatment in patients with growth retardation.

  • In patients with end-stage renal disease or kidney failure, treatment such as dialysis and kidney transplant can be an option. Pre-symptomatic diagnosis is possible in patients whose affected members of the family have been diagnosed.

  • Patients with advanced chronic kidney disease or at high risk of disease progression should undergo prompt monitoring and recommendation from the physician.

  • Blood pressure, growth parameters, and renal function should be checked promptly.

  • Evaluation for renal disease, liver function, and urine analysis is essential.

  • Nephrotoxic drugs such as NSAIDs and aminoglycosides should be avoided.

  • A pre-symptomatic diagnosis of the disease can help the patient to avoid higher risk and treat the initial phase of the disease.

Conclusion :

Juvenile Nephronophthisis is a genetic disease and requires a pre-symptomatic diagnosis to treat it well. In the case of the affected family member, the rest of the family should also be diagnosed with the same disease. Secondary infections such as influenza, pneumonia, and hepatitis B should be taken care of by vaccination. Monitoring of the disease as soon as diagnosed should be done at least once a year.

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Dr. Manzoor Ahmad Parry
Dr. Manzoor Ahmad Parry

Nephrology

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