Papillorenal syndrome overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Shivam Singla, M.D.[2]
Overview
Papillorenal syndrome is an autosomal dominant genetic disorder marked by underdevelopment (hypoplasia) of the kidney and colobomas of the optic nerve.[1]
The other name for papillorenal syndrome is Renal-coloboma syndrome. It is a rare disorder that affects the development of kidneys and the eyes. Affected kidneys are usually small or underdeveloped and may progress to ESRD when the kidneys are no longer able to filter the fluids. One or both the kidneys can be involved In the eyes, various malformations noted are malformed optic nerve and occasionally a hole in the retina known as coloboma. Some of the affected individuals may experience vision loss. Hence the name is given as Renal-coloboma syndrome. Other less common symptoms associated with the disease include vesicoureteral reflux, loose abnormal joints, numerous kidney cysts, and minimal hearing loss.
Historical Perspective
Papillorenal syndrome for which another term is Renal-coloboma syndrome (RCS). This condition usually consisting of renal anomalies plus optic nerve dysplasia. It is transmitted to future generations in an Autosomal dominant fashion. First clearly described by Weaver al in 1988. In two brothers having ESRD with coloboma in the eyes. In 1995, the association of dominant mutations in the PAX2 gene with RCS was made. It was studied in a two-generation family having renal dysplasia, coloboma of the optic nerve, and also the presence of vesicoureteral reflux. There are different opinions regarding the name of this condition between the observers. Papillorenal syndrome is a combination of renal and ocular anomalies. Eccles and Schimmenti, 1999; Negrisolo et al., 2011 summarized Less common findings associated with the expression of the PAX2 gene in numerous tissues with the disease include hearing loss, CNS anomalies, joint problems, ligament laxity, soft skin.
Pathophysiology
The known cause of the Papillorenal syndrome is mutation of a copy of the PAX2 gene, a gene which is important in the development of both the eye and the kidney. However, approximately half of patients with Papillorenal syndrome do not have defects in the Pax2. This suggests that other genes play a role in the development of the syndrome, though few downstream effectors of Pax2 have been identified.
Papillorenal syndrome differential diagnosis
The renal coloboma syndrome differentials include most of the disease with renal and ocular anomalies. The numerous important differentials are
- CHARGE Syndrome that includes characteristic five features of the disease including Coloboma, Heart Abnormalities, Choanal Atresia, Growth and development Retardation, Genital Anomalies, Ear and hearing abnormalities. A lot of patients studied under Renal-coloboma syndrome do not have any sort of craniofacial anomalies that are typical of CHARGE Syndrome.
- Branchio-oto-renal syndrome- Renal hypoplasia in these patients makes this an important differential. Pt with PAX6 Mutations - significant overlap with eye findings in patients with PAX6 gene mutation make it an important differential but the renal anomalies that are typical for RCS are absent in these patients.
- COACH Syndrome or Joubert - Important differential due to the presence of both renal abnormalities and coloboma in these patients. However, patients with Renal-coloboma syndrome does not have any developmental abnormality, cerebellar abnormalities, and/or hepatic dysfunction.
- Cat Eye Syndrome - This genetic abnormality is having symptomatic overlap with Renal-coloboma syndrome but the Iris coloboma that is typical for RCS is usually not observed in this disorder.
Epidemiology and demographics
The Prevalence of the disease and the prevalence at birth is still unknown. In a study conducted in 90 families, they found 177 mutation-positive cases. The number of individuals with mutation-negative is not known in that study. The conclusion derived showed no ethnic predilection for the disease. The major component found in the causation of RCS is PAX2 gene (10q24) in half of the patients with renal and optic nerve abnormalities.
Risk Factors
The pathophysiology and the risk factors responsible for the development of Renal-coloboma syndrome is mainly genetic and related to the expression of PAX 2 gene. So the genetic inheritance is the main risk factor or the important determinant in the causation of Renal-coloboma syndrome. This genetic syndrome keeps on clustering in the future generations.
The environmental risk factors that impact the pregnancy like alcohol and some drugs may also contribute to the development of Renal-coloboma syndrome. In conclusion, RCS leads to the abnormal development of organs like kidney and eyes during the pregnancy period. The abnormal development of eyes usually happens in the third trimester during that time the eyes are formed. The abnormalities usually occur due to the impairment in the closure of the optic disc. It usually depends on which specific part or areas of optic fissure fails to close.