Introduction
Myeloma kidney, also known as myeloma-associated renal impairment or myeloma cast nephropathy, is a serious complication that arises in the context of multiple myeloma, a hematological malignancy affecting plasma cells. Multiple myeloma is characterized by the uncontrolled increase in the abnormal plasma cells in the bone marrow, leading to the overproduction of monoclonal proteins, or M-proteins, and their release into the bloodstream. These M-proteins can accumulate and form deposits in various organs, including the kidneys, leading to renal dysfunction.
What Is Multiple Myeloma?
Myeloma is a cancer of the bone marrow. The bone marrow is the spongy space inside bones where blood is made. The marrow is present in all bones, and the majority of it is found in large bones such as ribs, backbone, pelvis, and bones of arms and legs. The bone marrow helps in the formation of various blood cells in the body, and one of them is plasma cells. These plasma cells are an essential part of the immune system that helps in the formation of antibodies that fight off the disease or pathogenic organisms in the body. In patients affected with multiple myeloma, the plasma cells are abnormal and become cancerous, which means they start growing uncontrollably and make abnormal proteins.
These abnormal antibodies and plasma cells can cause various complications in the body, such as bone disease, anemia, renal failure, increased risk of infection, and high levels of calcium.
What Is Myeloma Kidney?
Kidney failure is one of the most common complications of multiple myeloma and can affect kidneys in several ways. In 20 to 40 percent of patients where multiple myeloma is diagnosed initially may have kidney failure. Multiple myeloma can also affect the filtration process of kidneys by impacting the glomerulus (filter), tubules, or issues of the kidney. The effect of myeloma on the tubules of the kidney is commonly referred to as myeloma kidney.
What Are the Causes and Pathophysiology of Myeloma Kidney?
The main cause of myeloma kidney is the overproduction of monoclonal immunoglobulin, particularly the light chains (Bence Jones proteins) by malignant plasma cells. These light chains are small proteins that can easily pass through the glomerular filtration barrier in the kidneys and accumulate within the renal tubules, leading to kidney damage and dysfunction.
The renal tubules are responsible for reabsorbing essential substances and eliminating waste products from the blood, and when these tubules are inundated with light chains, they become dysfunctional, resulting in myeloma in the kidney.
What Are the Clinical Manifestations of Myeloma Kidney?
The clinical presentation of myeloma kidney can vary widely, depending on the degree of kidney damage and other contributing factors. Some common signs and symptoms include -
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Proteinuria - The hallmark feature of the myeloma kidney is the presence of protein in the urine, which is called proteinuria. This can be detected by a simple urine test and can range from mild to severe.
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Hematuria - Blood in the urine is another frequent manifestation caused by the damage to the kidney's filtration system.
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Decreased Urine Output - As the kidney function declines, there may be a reduction in urine output, leading to oliguria (low urine volume) or even anuria (absence of urine production).
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Edema - The collection of fluid in the tissues of the body causing swelling is called edema, especially in the ankles and legs.
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Fatigue and Weakness - Anemia (blood disorder) may develop due to the impact of cancer on the bone marrow, resulting in fatigue and weakness.
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Bone Pain and Fractures - Multiple myeloma can cause bone lesions, leading to bone pain and increasing the risk of fractures.
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Hypercalcemia - It means high levels of calcium in the blood, which can cause symptoms like nausea, excessive thirst, frequent urination, and confusion.
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Hyperviscosity Syndrome - In some cases, the excessive M protein can cause an increase in blood viscosity, leading to symptoms such as blurred vision, headaches, and neurological issues.
What Are the Risk Factors for Kidney Failure in Multiple Myeloma?
The risk of kidney failure increases with the severity of the myeloma and the duration of the disease before initiating the treatment. Factors that may increase the chances of kidney failure in people with multiple myeloma may include -
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Underlying chronic kidney disease.
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Abnormal electrolyte levels.
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The age of 65 to 70 years is the median age for multiple myeloma diagnosis, and older age is also a risk factor for kidney disease.
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Use of non-steroidal anti-inflammatory drugs (NSAIDs).
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Underlying medical diseases like high blood pressure (hypertension) and diabetes.
What Is the Diagnosis of Myeloma Kidney?
The diagnosis of myeloma kidney involves a comprehensive evaluation of the patient's medical history, physical examination, laboratory tests, and imaging studies. Some essential diagnostic steps include -
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Blood and Urine Tests - Blood tests help assess kidney function, detect the presence of M protein, and evaluate calcium levels. A 24-hour urine collection is performed to quantify proteinuria and assess the levels of Bence Jones proteins.
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Kidney Biopsy: A kidney biopsy is essential to confirm myeloma kidney and differentiate it from other kidney diseases with similar clinical features. A small tissue sample is extracted from the kidney and examined under a microscope.
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Imaging Studies: X-rays, CT scans, or MRIs are conducted to evaluate the extent of bone lesions and assess the overall status of multiple myeloma.
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Bone Marrow Biopsy: To establish the diagnosis of multiple myeloma, a bone marrow biopsy is performed to analyze the percentage of plasma cells and detect any chromosomal abnormalities.
What Are the Treatment Options for Myeloma Kidney?
The management of myeloma kidney requires a multidisciplinary approach involving oncologists, hematologists, nephrologists, and other healthcare professionals. The treatment plan is tailored based on the severity of kidney involvement, the stage of multiple myeloma, and the overall health of the patient. The main treatment options include -
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Chemotherapy - This remains the most essential part of multiple myeloma treatment. It aims to reduce the population of malignant plasma cells, subsequently lowering the production of M protein.
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Stem Cell Transplantation - For eligible patients, chemotherapy followed by stem cell transplantation may be recommended to achieve the desired response.
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Targeted Therapies - Novel targeted therapies, such as proteasome inhibitors (Bortezomib), immunomodulatory drugs (Lenalidomide), and monoclonal antibodies (Daratumumab), have shown promising results in improving outcomes in multiple myeloma.
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Plasmapheresis - In severe cases of myeloma kidney with acute kidney injury, plasmapheresis may be used to remove excessive light chains from the blood, providing rapid relief from kidney damage.
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Supportive Care - Patients with myeloma kidney may require supportive measures, such as intravenous fluids to maintain adequate hydration and medications to manage symptoms like anemia and hypercalcemia.
Conclusion
Myeloma kidney is a serious complication of multiple myeloma that can lead to significant kidney damage and dysfunction. Early detection and a comprehensive treatment approach are crucial in managing this condition and improving patient outcomes. By understanding the causes, clinical manifestations, diagnostic procedures, treatment options, and prognosis of myeloma kidney, healthcare professionals can provide timely and effective interventions to minimize renal complications and optimize the overall care of patients with multiple myeloma. Additionally, ongoing research and advancements in treatment modalities gave hope for better outcomes and improved quality of life for individuals affected by this complex and challenging condition.
