Glomerular diseases: A condition overview and infographic
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What are glomerular diseases?
Your kidneys have about one million tiny filter units called nephrons.
Each nephron has a glomerulus, meaning there are over one million of them too. More than one glomerulus are called glomeruli. Glomeruli work like strainers used in cooking. While blood moves through them, they let waste and extra water pass into the nephrons to make urine. At the same time, they hold back the protein and blood that your body needs.
Many diseases affect kidney function by attacking the glomeruli. When the glomeruli become damaged and cannot do their job, it is called glomerular disease. Glomerular diseases cover many conditions with many different causes,¹ these include: complement 3 glomerulopathy (C3G) and immune complex membranoproliferative glomerulonephritis (IC-MPGN) both of which fall under the umbrella term of MPGN .
Signs and symptoms
Blood in the urine (haematuria): Glomerular disease can cause your glomeruli to leak blood into urine. It can also cause high blood pressure (hypertension).²
Protein in the urine (proteinuria): Glomerular disease can cause your glomeruli to leak protein into urine. Urine may be foamy because of the protein.³
Edema (swelling from fluid): Glomerular disease can cause swelling in areas such as the hands, ankles, or around the eyes.⁴ It can also cause joint pain and rashes.⁵
Chronic fatigue: Glomerular disease can also cause shortness of breath, fatigue, loss of appetite, weight loss and yellowing of the whites of the eyes or the skin.⁶
C3G and IC-MPGN
C3G and IC-MPGN are two sub-types of glomerulopathies that fall under the umbrella of glomerular diseases in particular membranoproliferative glomerulonephritis (MPGNs).
C3G is typically a overactivation of the alternative complement pathway, leading to the deposition of the complement protein C3 within the glomeruli. This abnormal accumulation of C3 disrupts the normal filtration function of the kidneys, ultimately resulting in proteinuria, potential edema (swelling due to excess fluid), and a decline in kidney function. There are two types of C3G: dense deposit disease (DDD) and C3 glomerulonephritis (C3GN).
The risk of progression to end-stage kidney disease is high for C3G, with the 5-10-year risk estimated to be over 50%.⁹
IC-MPGN has many similarities, however, IC-MPGN may also occur secondary to other factors such as infection, autoimmune diseases or malignancy. This is classified as secondary. IC-MPGN without a known secondary cause is referred to as primary IC-MPGN.
Diagnosis and symptom management
Diagnosis of C3G and IC-MPGN typically involves a detailed patient history, physical examination, bloodwork and ultimately a kidney biopsy. The defining differentiator between C3G and IC-MPGN is the presence and intensity of C3 and immunoglobulin deposits as seen on histology of biopsied tissue.
Symptom management of both C3G and IC-MPGN varies depending on the stage of disease and in C3G and primary IC-MPGN typically involves treatments to reduce symptoms of the complement overactivation, which, may include steroids or immunosuppressants. In secondary IC-MPGN, treating the underlying causation such as infection, autoimmune disease or malignancy can result in improvement in the kidney.
C3G and IC-MPGN are estimated to affect up to 18,000 individuals in the US and EU4* alone.9
References
1. https://www.kidney.org/kidney-topics/understanding-glomerular-diseases
2, 3, 4. https://my.clevelandclinic.org/health/diseases/5993-glomerular-diseases?form=MG0AV3
5, 6. https://www.nhs.uk/conditions/glomerulonephritis/?form=MG0AV3
7. https://academic.oup.com/ndt/article/38/2/283/6378885
8. Information from ‘Navigating the complexities of glomerular disease—C3G and IC-MPGN: an HCP perspective’
9. ClearView. Data on file; 2019.
10. Smith RJH, et al. Nat Rev Nephrol. 2019 10. 15(3):129-143.
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