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Patients With Infantile Nephropathic Cystinosis in Germany and Austria: A Retrospective Cohort Study
Nina O'Connell1, Jun Oh2, Klaus Arbeiter3
1Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany.
Insights
Early diagnosis of infantile nephropathic cystinosis (INC) and prompt cysteamine treatment significantly improves kidney survival. While cystine-depleting therapy met international standards, patient growth requires better management.
Area of Science:
- Pediatric Nephrology
- Lysosomal Storage Disorders
- Rare Diseases
Background:
- Infantile nephropathic cystinosis (INC) is a rare genetic disorder causing progressive kidney disease and systemic complications.
- It presents a significant challenge for affected families and healthcare providers.
- No comprehensive clinical course studies for INC patients in Germany and Austria were available.
Purpose of the Study:
- To analyze the clinical course of infantile nephropathic cystinosis in Germany and Austria.
- To evaluate diagnostic timelines, treatment efficacy, and long-term outcomes.
- To identify factors influencing renal survival in INC patients.
Main Methods:
- Retrospective cohort study of 74 INC patients across eleven centers.
- Data collection included diagnosis age, CKD stage, leukocyte cystine levels (LCL), extrarenal manifestations, and treatments.
- Kaplan-Meier analysis assessed age at kidney replacement therapy (KRT) initiation.
Main Results:
- Median diagnosis age was 15 months; earlier diagnosis (before 18 months) correlated with significantly later KRT initiation (21 vs. 13 years).
- Cysteamine therapy achieved target LCLs in 69.2% of measurements, indicating adherence to international standards.
- Median height was at the 7th percentile, with 40.5% of patients below the 3rd percentile, highlighting growth issues.
Conclusions:
- Early diagnosis and cystine-depleting therapy are crucial for improved renal survival in INC.
- Treatment adherence and cystine levels met international benchmarks, but significant interindividual variability exists.
- Future efforts should focus on optimizing patient growth and managing extrarenal manifestations more effectively.
Background:
Infantile nephropathic cystinosis (INC) is a rare lysosomal storage disorder resulting in progressive chronic kidney disease (CKD) and a variety of extrarenal manifestations. This orphan disease remains a challenge for patients, their families and health care providers. There is currently no comprehensive study on patients' clinical course in Germany and Austria.
Methods:
A retrospective cohort study including 74 patients at eleven centers of care was conducted. Data on time of diagnosis, CKD stage, leukocyte cystine levels (LCL), extrarenal manifestations, and treatment was collected from medical charts and subsequently analyzed using explorative statistics. Age at initiation of kidney replacement therapy (KRT) was evaluated by Kaplan-Meier analyses for different groups of patients.
Results:
Patients were diagnosed at a median age of 15 months (IQR: 10-29, range: 0-110), more recent year of birth was not associated with earlier diagnosis. Oral cystine-depleting therapy (i.e., cysteamine) was prescribed at a median dose of 1.26 g/m2 per day (IQR: 1.03-1.48, range: 0.22-1.99). 69.2% of all 198 LCL measurements of 67 patients were within the desired target range (≤ 1 nmol cystine/mg protein). Median time-averaged LCLs per patient (n = 65) amounted to 0.57 nmol cystine/mg protein (IQR: 0.33-0.98, range: 0.07-3.13) when considering only values at least 1 year after initiation of therapy. The overall median height of 242 measurements of 68 patients was at the 7th percentile (IQR: 1-25, range: 1-99). 40.5% of the values were ≤ the 3rd percentile. Patient sex and year of birth were not associated with age at initiation of KRT, but patients diagnosed before the age of 18 months required KRT significantly later than those patients diagnosed at the age of ≥ 18 months (p = 0.033): median renal survival was 21 years (95% CI: 16, -) vs. 13 years (95% CI, 10, -), respectively.
Conclusion:
Early diagnosis and initiation of cystine depleting therapy is important for renal survival in children with INC. Cysteamine doses and LCL showed that treatment in this cohort met international standards although there is great interindividual variety. Patient growth and other aspects of the disease should be managed more effectively in the future.
