Nephronopthisis is a very rare autosomal recessive genetic disorder of the kidney. I do not have a great deal of experience with this disease. Experts at the institutions that you mention should be able to provide a specific diagnosis but there is no known treatment other than to try and correct the electrolyte abnormalities that you describe. You can review the information on the National Institutes of Health web site at: https://ghr.nlm.nih.gov/condition/nephronophthisis
I suggest that you continue to work with the experts at these tertiary medical centers for advice and treatment.