Response to "Nephronophthisis Is an Important Differential Diagnosis of Nonspecific Interstitial Nephritis in Adults".

The Authors Reply:

We thank Gillion et al. for their interesting contribution in response to our article that perfectly matches our view and strengthens our message.

The authors’ case series underlines that nephronophthisis needs to be considered for differential diagnosis of interstitial nephritis in adults even in the absence of polyuria, proteinuria, hematuria, and/or extrarenal symptoms. Nephronophthisis belongs to the group of cystic kidney diseases and ciliopathies characterized by tubulointerstitial findings, such as fibrosis. Remarkably, kidney cysts if any usually only occur late during the clinical course. A comprehensive genetic testing approach is crucial; only for nephronophthisis, we are aware of >30 genes currently known.

The patients described by Gillion et al. emphasize the increasing importance of reverse phenotyping by genetics. There is growing evidence that a considerable fraction of adult nephrology patients currently classified as nongenetic actually harbor a monogenic cause for their kidney disease. This report also nicely illustrates that knowledge of the underlying genotype has direct clinical implications for patients and families and is useful in terms of therapy, care, and prognosis.