Nephronophthisis is a genetic disorder of the kidneys which affects children.[3] It is classified as a medullary cystic kidney disease. The disorder is inherited in an autosomal recessive fashion and, although rare, is the most common genetic cause of childhood kidney failure. It is a form of ciliopathy.[4] Its incidence has been estimated to be 0.9 cases per million people in the United States, and 1 in 50,000 births in Canada.[5]
Signs and symptoms
Infantile, juvenile, and adolescent forms of nephronophthisis have been identified. Although the range of characterizations is broad, people affected by nephronophthisis typically present with polyuria (production of a large volume of urine), polydipsia (excessive liquid intake), and after several months to years, end-stage kidney disease, a condition necessitating either dialysis or a kidney transplant in order to survive.[1] Some individuals with nephronophthisis also have so-called "extra-renal symptoms" which can include tapetoretinal degeneration, liver problems, oculomotor apraxia, and cone-shaped epiphysis (Saldino-Mainzer syndrome).[6][7]
Cause
Nephronophthisis is characterized by fibrosis and the formation of cysts at the cortico-medullary junction, it is an autosomal recessive disorder which eventually leads to terminal kidney failure.[8]
Pathophysiology
Mechanism of nephronophthisis indicates that all proteins mutated in cystic kidney diseases express themselves in primary cilia. NPHP gene mutations cause defects in signaling resulting in flaws of planar cell polarity. The ciliary theory indicates that multiple organs are involved in NPHP (retinal degeneration, cerebellar hypoplasia, liver fibrosis, and intellectual disability).[9]
NPHP2 is infantile type of nephropthisis[check spelling] and sometimes associated with situs inversus this can be explained by its relation with inversin gene. NPHP1, NPHP3, NPHP4, NPHP5, and NPHP6 are sometimes seen with retinitis pigmentosa, this particular association has a name, Senior-Loken syndrome.[11]
Diagnosis
The diagnosis of nephronophthisis can be obtained via a kidney ultrasound, family history and clinical history of the affected individual according to Stockman, et al.[2]
Nephronophthisis occurs equally in both sexes and has an estimate 9 in about 8 million rate in individuals. Nephronophthisis is the leading monogenic cause of end-stage kidney disease.[12]
^page 831, Chapter 35, in: Avner, Ellis D.; Harmon, William; Niaudet, Patrick; Yoshikawa, Norishige (2009-08-20). Pediatric Nephrology (Avner, Pediatric Nephrology). Springer. ISBN978-3-540-76327-7. (stating the incidence in the United States as 9 per 8.3 million people.
^Badano, Jose L.; Mitsuma, Norimasa; Beales, Phil L.; Katsanis, Nicholas (2006). "The Ciliopathies: An Emerging Class of Human Genetic Disorders". Annual Review of Genomics and Human Genetics. 7: 125–48. doi:10.1146/annurev.genom.7.080505.115610. PMID16722803.
^Hildebrandt, Friedhelm (2009). "Nephronophthisis". In Lifton, Richard P.; Somlo, Stefan; Giebisch, Gerhard H.; et al. (eds.). Genetic Diseases of the Kidney. Academic Press. pp. 425–46. ISBN978-0-08-092427-4.