In a monocentric, later multicentric prospective approach the FOrMe registry (The German Focal Segmental Glomerulosclerosis and Minimal Change Disease Registry) aims to generate a longitudinal cohort of 150 pediatric cases of idiopathic nephrotic syndrome and 350 adult cases of biopsy-proven Minimal Change Disease (MCD) or Focal and Segmental Glomerular Sclerosis (FSGS) over 10 years. The registry will provide a repository for biomaterials such as blood samples, DNA, urine, feces, and tissue biopsies that will be accessible to collaborators to facilitate future research on pathogenesis, diagnostics, and treatment.

Idiopathic Nephrotic Syndrome is characterized by proteinuria, volume retention, hyperlipidemia, hypoalbuminemia. As Minimal Change Disease (MCD) represents by far the most prevalent underlying diagnosis in children older than 1 year, a kidney biopsy is usually deferred in these cases. In adolescence and adults, a kidney biopsy is crucial for the diagnosis because MCD and FSGS account for only 10-15 and 12-35 percent of all cases of nephrotic syndrome respectively. Pathomechanisms as well as optimal treatment remain elusive as systematic trials are scarce and hampered by low incidence and heterogenicity of the clinical presentation. To bridge this informational gap, the investigators identified the need for a German registry of pediatric and adult patients with idiopathic nephrotic syndrome (in children) and biopsy-proven MCD/FSGS (in adults).

The registry will record clinical data of participants regarding basic demographics, initial presentation, hereditary traits, disease course and treatment modalities as well as quality of life, concomitant diseases, and comedication. During the initial visit and to a lesser intent on follow-up visits, biomaterials (blood, urine, DNA, feces, tissue) will be collected and stored in a state-of-the art biobank. This material will be available to collaborators to support research on idiopathic nephrotic syndrome and MCD/FSGS. By the time of completion, the registry will provide data on clinical courses and outcome of approximately 500 patients that can easily be correlated with biomaterials giving insight into risk factors, prognostic parameters, and association with comorbidities.

Tissue sections of all patients that undergo kidney biopsy (all adult and some pediatric patients) will be digitalized, annotated, and analyzed by a panel of nephropathologists. Histopathologic features will be individually assessed and scored according to a set of descriptors that was developed and is used by the American NEPTUNE (Nephrotic Syndrome Study Network).

Inclusion Criteria (cohort A):

• written informed consent
• 17 or less years of age
• idiopathic nephrotic syndrome

Inclusion Criteria (cohort B):

• written informed consent
• older or equal to 18 years of age
• biopsy-proven primary or secondary FSGS or MCD or biopsy-proven recurrence of disease in kidney transplant.

Exclusion Criteria (both cohorts):

• Prior kidney transplant without biopsy-proven recurrence
• A clinical diagnosis of other glomerular disease resulting in secondary MCD or FSGS as judged by the treating physicians.
• Refusal to provide written informed consent
• (Anticipated) incompliance with visit schedule

Pediatric patients until 18 years of age presenting with or diagnosed with idiopathic nephrotic syndrome or a biopsy-proven diagnosis of MCD or FSGS. Candidate participants need to be willing to provide written informed consent.

Adult patients 18 years and above with a biopsy-proven diagnosis of primary or secondary FSGS or MCD. Candidate participants need to be willing to provide written informed consent.

Biosamples as well as patient data will be available to collaborators after revision of research application by a steering committee.

5-15 years

Actively contributing to registry and approval by international steering committee.