Senior Director Pfizer, Inc. New York, United States
Background: Rare kidney diseases cause progressive decline in kidney function, and most do not have adequate treatment options. However, gaps remain in disease understanding due to scarce data in sufficient patient populations. Access to large, geographically representative registries enable the conduct of real-world studies to better understand rare disease patients.
Objectives: To describe the prevalence, demographics, clinical characteristics, and treatment of rare kidney disease patients in the United Kingdom (UK).
Methods: This retrospective study used the UK National Registry of Rare Kidney Diseases (RaDaR) from 2010 to 2022, which collects data from 107 renal care centers. Point prevalence of select rare kidney conditions were estimated, overall and stratified by sex and age groups. Patients’ demographics, clinical characteristics, and treatments were described. Nine rare kidney conditions were assessed, including Focal segmental glomerulonephritis (FSGS), IgA nephropathy (IgAN), Membranous nephropathy (MN), Minimal change nephropathy (MCD), Steroid resistant nephrotic syndrome (SRNS), Steroid sensitive nephrotic syndrome (SSNS), Autosomal dominant polycystic kidney disease (ADPKD), Autosomal recessive polycystic kidney disease (ARPKD), and Alport syndrome.
Results: The estimated prevalence for FSGS was 1.6/100k (95% CI: 1.5 to 1.6), IgAN was 6.5/100k (95% CI: 6.4 to 6.5), MN was 3.7/100k (95% CI: 3.6 to 3.7), MCD was 1.3/100k (95% CI: 1.3 to 1.4), SRNS was 0.4/100k (95% CI: 0.4 to 0.4), SSNS was 1.5/100k (95% CI: 1.5 to 1.6), ADPKD was 11.8/100k (95% CI: 11.7 to 11.9), ARPKD was 0.4/100k (95% CI: 0.3 to 0.4), and Alport syndrome was 1.4/100k (95% CI: 1.4 to 1.4). Prevalence between sexes were generally equal for all diseases, except for IgAN and MN where prevalence for males were roughly three-fold and two-fold higher, respectively.
Among disease populations, median diagnosis age for MN was greatest at 52 years (IQR: 30 to 65) and lowest for ARPKD at 1 year (IQR: 0 to 20). Median baseline urine protein creatinine ratio (UPCR) were elevated (defined as greater than 3 g/g) in FSGS (5.3 g/g; IQR: 2.7 to 9.4), MCD (6.1 g/g; IQR: 2.4 to 10), and MN (6.0 g/g; IQR: 3.2 to 8.8). Median estimated glomerular filtration rate (eGFR) was below 60 ml/min for IgAN (40 ml/min; IQR: 22 to 69) and ARPKD (52 ml/min; IQR: 33 to 75). Diseases had differing rates of corticosteroid use on day of diagnosis, ranging from 1.1% for ADPKD to 51.4% for SSNS and calcineurin inhibitor use ranged from 1.7% for ADPKD and Alport syndrome and 26.3% for SRNS patients.
Conclusions: Registries provide a rich and valuable source of information to estimate prevalence and describe clinical characteristics and treatments of patient populations, particularly in rare conditions where data is scarce.
