Nephronophthisis and related syndromes.

PURPOSE OF REVIEW: Nephronophthisis (NPHP) is an autosomal recessive cystic kidney disease and is one of the most common genetic disorders causing end-stage renal disease (ESRD) in children and adolescents. NPHP is a genetically heterogenous disorder with 20 identified genes. NPHP occurs as an isolated kidney disease, but approximately 15% of NPHP patients have additional extrarenal symptoms affecting other organs [e.g. eyes, liver, bones and central nervous system (CNS)]. The pleiotropy in NPHP is explained by the finding that almost all NPHP gene products share expression in primary cilia, a sensory organelle present in most mammalian cells. If extrarenal symptoms are present in addition to NPHP, these disorders are classified as NPHP-related ciliopathies (NPHP-RC). This review provides an update about recent advances in the field of NPHP-RC.

RECENT FINDINGS: The identification of novel disease-causing genes has improved our understanding of the pathomechanisms contributing to NPHP-RC. Multiple interactions between different NPHP-RC gene products have been published and outline the interconnectivity of the affected proteins and shared pathways.

SUMMARY: The significance of recently identified genes for NPHP-RC is discussed and the complex role and interaction of NPHP proteins in ciliary function and cellular signalling pathways is highlighted.