OVERVIEW

What is light chain nephropathy?

Light chain nephropathy (LCN) refers to the deposition of large amounts of light chain proteins in the kidneys, leading to renal tubular damage, intratubular cast formation, and obstruction, subsequently causing acute or chronic kidney disease.

Chemotherapy is often required, and the prognosis is generally poor.

Is light chain nephropathy common?

Light chain nephropathy is a rare disease, mostly seen in patients with myeloma. The age of onset is usually over 50, and it is more common in males than females, with a male-to-female ratio of approximately 4:1.

With increased awareness and improved diagnostic methods for this disease, its incidence has also risen.

SYMPTOMS

What are the common manifestations of light chain nephropathy?

• Renal manifestations are often the sole or initial symptom of light chain nephropathy. Some patients present with chronic interstitial nephritis syndrome, while others exhibit proteinuria, microscopic hematuria, nephrotic syndrome, or mild to moderate hypertension and anemia.

• Renal failure occurs early and progresses rapidly to end-stage renal failure.

• In addition to kidney damage, the heart, liver, and spleen are frequently affected. Symptoms may include hepatomegaly, portal hypertension, cardiomegaly, heart failure, and arrhythmias.

• A small number of patients may experience central nervous system, pulmonary, or skin involvement.

CAUSES

What are the possible causes of light chain nephropathy?

Light chain nephropathy is a type of renal damage caused by dysimmunoglobulinemia:

• Dysimmunoglobulinemia refers to a group of diseases caused by abnormal malignant proliferation of plasma cells and their precursor B lymphocytes, which secrete large amounts of homogeneous abnormal immunoglobulins, leading to excessive monoclonal immunoglobulins or their heavy and light chains in the blood. When large amounts of light chain proteins deposit in the kidneys, causing proteinuria and renal dysfunction, light chain-induced renal damage occurs.

• Light chain nephropathy often manifests as renal involvement in conditions such as multiple myeloma, monoclonal gammopathy of renal significance, and amyloidosis. In autopsy or biopsy studies, light chain cast nephropathy is the most common finding in patients with multiple myeloma and clinical renal involvement, accounting for 33% to 60% or more of cases.

DIAGNOSIS

How is light chain nephropathy diagnosed?

Initial diagnosis is mainly based on clinical manifestations and laboratory tests, while definitive diagnosis usually relies on renal biopsy pathology examination.

What tests are needed for light chain nephropathy?

In addition to routine general tests (such as blood tests, kidney function tests, etc.), a renal biopsy is required.

Renal biopsy pathology can confirm light chain nephropathy. In addition to conventional light microscopy (including HE, PAS, Masson, and PASM staining), immunofluorescence, and electron microscopy, special pathological tests such as Congo red staining, potassium permanganate pretreatment test, and monoclonal free light chain (Kappa and Lambda) detection are also performed. A positive result usually confirms the diagnosis.

What diseases should light chain nephropathy be differentiated from?

• Differentiation from other renal damage caused by abnormal globulinemia: such as renal damage from macroglobulinemia, cryoglobulinemia, or heavy chain disease;

• Differentiation from other light chain deposition-related renal damage: such as light chain amyloidosis or multiple myeloma.

TREATMENT

Which department should be consulted for light chain nephropathy?

Generally, it is necessary to visit the nephrology department of each hospital.

How should light chain nephropathy be treated?

The prognosis of light chain nephropathy is poor, and there is currently no specific treatment. Chemotherapy is generally the main approach.

• Some patients with mild or moderate kidney damage may maintain stable or improved kidney function after chemotherapy with melphalan, prednisone, cyclophosphamide, etc.

• For patients who develop acute renal failure, plasma exchange therapy should be performed promptly to reduce the damage caused by urinary toxins to the body.

DIET & LIFESTYLE

What should patients with light chain nephropathy pay attention to in daily life?

• In addition to chemotherapy, patients with light chain nephropathy should adopt a low-protein, high-quality protein diet. For example, consume more animal proteins with high amino acid utilization such as eggs, milk, and fresh fish, while reducing intake of plant proteins with low amino acid utilization like legumes, to alleviate kidney burden.

• At the same time, ensure adequate intake of essential amino acids, minerals, and vitamins, particularly vitamin B₆, folic acid, iron, zinc, and other trace elements, to prevent malnutrition.

• In cases of renal insufficiency, restrict salt and water intake, and regularly monitor blood pressure and observe changes in urine output.

• Maintain regular bowel movements, avoid infections, overexertion, and the use of nephrotoxic drugs to prevent worsening kidney damage.

PREVENTION

How to prevent light chain nephropathy?

Light chain nephropathy is a monoclonal immunoglobulin disorder caused by abnormal proliferation of lymphocytes and plasma cells, which produce excessive light chains that deposit in the kidneys, leading to proteinuria and renal dysfunction. There are no specific preventive measures in daily life.