OVERVIEW

What is renal amyloidosis?

Amyloidosis is a pathological concept referring to a group of diseases caused by the deposition of amyloid proteins in the extracellular matrix, leading to tissue and organ damage at the deposition sites. It can affect multiple organs and tissues, including the kidneys, heart, liver, skin, soft tissues, peripheral nerves, lungs, and glands.

Renal amyloidosis occurs when amyloid deposits affect the kidneys, primarily manifesting as nephrotic syndrome symptoms such as proteinuria and hypoalbuminemia. Hematuria is uncommon, but the condition may be accompanied by involvement of other organs, such as the heart, gastrointestinal tract, or skin.

Currently, there is no specific cure for this disease. However, treatments aimed at reducing the production or promoting the breakdown of amyloid precursor proteins can improve patient survival rates and preserve organ function.

Without timely intervention, complications such as kidney failure, heart failure, or sudden death may occur. Although isolation is unnecessary, the patient's quality of life can be severely impacted.

Is renal amyloidosis common?

Renal amyloidosis is relatively rare and is more commonly seen in middle-aged and elderly men.

What are the types of renal amyloidosis?

• Based on the extent of organ involvement: It can be classified into localized renal amyloidosis (affecting a single organ) and systemic renal amyloidosis (affecting multiple organs).

• Based on the type of amyloid protein involved: Common types include light-chain amyloidosis (AL type) and heavy-chain amyloidosis (AA type), with some cases being hereditary amyloidosis (AF type).

• Based on etiology: It can be categorized as:

• Secondary amyloid deposition, associated with chronic suppurative diseases, chronic destructive diseases, immune disorders, and certain tumors.

• Primary amyloid deposition, where no underlying cause can be identified.

• Familial hereditary amyloid deposition.

• Amyloid deposition limited to a single organ or tissue. Clinically, primary amyloid deposition is the most common.

SYMPTOMS

What are the common symptoms and manifestations of renal amyloidosis?

This disease is a systemic disorder. In addition to kidney involvement, other organs may also be affected. Clinical manifestations vary depending on the affected organs, severity of the condition, and location of the lesions. Secondary cases may present differently due to underlying diseases.

In some cases, systemic involvement is not obvious, and kidney involvement may be the first manifestation.

• Renal manifestations: Divided into 4 stages.

• Preclinical stage: No subjective symptoms, physical signs, or abnormal laboratory findings. Diagnosis can only be made through renal biopsy. This stage may last for 5–6 years.

• Proteinuria stage: Proteinuria is a common early symptom. The severity of proteinuria does not necessarily correlate with the extent of amyloid deposition in the kidneys. Microscopic hematuria is rare, and hypertension may occur.

• Nephrotic syndrome stage: Characterized by massive proteinuria, hypoalbuminemia, and edema. Hyperlipidemia is less common, and some patients may only have long-term mild proteinuria. Disease progression is rapid during this stage, and the prognosis is poor.

• Uremia stage: Following nephrotic syndrome, progressive renal dysfunction occurs. Up to half of patients develop azotemia, and severe cases may die from uremia.

• Extrarenal manifestations: These depend on the sites of amyloid deposition.
  Cardiac involvement may lead to cardiomegaly, arrhythmias, and heart failure. Gastrointestinal involvement can cause constipation, diarrhea, macroglossia, hepatosplenomegaly, etc. Skin involvement may present with ecchymosis, pigmentation, or skin thickening.

How does renal amyloidosis progress?

The clinical manifestations of this disease are diverse, with an insidious onset. Accurate diagnosis is challenging, misdiagnosis rates are high, and the prognosis is poor. It often progresses rapidly to end-stage renal failure.

What diseases can renal amyloidosis cause?

Nephrogenic diabetes insipidus, hyperkalemia, renal failure, congestive heart failure, fatal arrhythmias, portal hypertension, esophageal variceal bleeding, spontaneous liver rupture, dyspnea, pleural effusion, infections, etc.

CAUSES

What causes renal amyloidosis?

Renal amyloidosis occurs due to the continuous or repeated production of excessive amyloid precursor proteins or the generation of abnormal amyloid precursor proteins.

Abnormal amyloid precursor proteins arise from amino acid substitutions caused by genetic mutations or degradation of certain protein components. Different types of renal amyloidosis have distinct mechanisms, such as AL-type being associated with deposits formed by immunoglobulin light chains.

Over twenty proteins have been confirmed to cause renal amyloidosis, collectively referred to as amyloid precursor proteins.

Who is most commonly affected by renal amyloidosis?

Middle-aged and elderly men.

Is renal amyloidosis contagious?

No.

Is renal amyloidosis hereditary?

It has a certain genetic predisposition.

DIAGNOSIS

How to Diagnose Renal Amyloidosis?

When diagnosing renal amyloidosis, doctors primarily rely on pathological examinations.

• The possibility of renal amyloidosis should be considered under the following circumstances:

• New-onset proteinuria or nephrotic syndrome in individuals over 40 years old, especially when accompanied by involvement of other organs;

• Proteinuria or nephrotic syndrome in patients with chronic infectious diseases or rheumatoid arthritis;

• Heavy proteinuria in patients with multiple myeloma or other malignancies.

• Renal biopsy is the most reliable method for definitive diagnosis. Amyloid deposits detected in pathological examinations of other tissues (e.g., rectum, gums, tongue, oral mucosa, skin, tendons, or abdominal fat aspiration) can also confirm the diagnosis.
  Immunohistochemistry, immunoelectron microscopy, or mass spectrometry can identify the amyloid deposits in renal tissues.

What Tests Are Needed for Renal Amyloidosis?

• Blood tests: Including complete blood count, liver and kidney function tests, blood biochemistry, coagulation tests, serum protein electrophoresis, immunofixation electrophoresis, serum immunoglobulin assays, troponin, and brain natriuretic peptide (BNP). These evaluate the patient's general condition, disease typing, cardiac function, and pre-treatment assessment.

• Urine tests: Urinalysis, urine protein quantification, urine immunofixation electrophoresis, and 24-hour urine light chain measurement. These estimate protein loss, clinical staging, and disease typing.

• Bone marrow examination: Used for diagnosis and differential diagnosis.

• Tissue pathology: Such as renal biopsy or biopsies of other affected tissues to confirm diagnosis and typing.

• Imaging studies: Chest X-ray, skull and pelvic X-rays, etc.

• Others: Electrocardiogram (ECG), echocardiography, and abdominal ultrasound to assess cardiac function, kidney size, and potential liver involvement.

Which Diseases Are Easily Confused with Renal Amyloidosis? How to Differentiate?

This condition must be differentiated from fibrillary glomerulopathy, immunotactoid glomerulopathy, light chain deposition disease, and cryoglobulinemia. Distinction is based on the diameter and arrangement of fibrillar proteins observed under electron microscopy in biopsy samples.

TREATMENT

Which department should I visit for renal amyloidosis?

Nephrology.

Can renal amyloidosis heal on its own?

No.

How should renal amyloidosis be treated?

• General treatment:

• During the acute phase, bed rest is recommended, along with adequate calorie and vitamin intake.

• Patients with renal insufficiency should limit protein intake. Those with nephrotic syndrome should restrict salt, use diuretics, and receive human albumin infusions. Patients with renal failure may require renal replacement therapies such as peritoneal dialysis or hemodialysis.

• Patients with complications involving the heart, liver, or other organs should receive symptomatic and supportive treatment to improve organ function.

• The prognosis is poor, and there is currently no specific treatment. However, reducing amyloid precursor protein production or promoting its breakdown may improve survival rates and preserve organ function.

• There is no effective treatment for primary amyloidosis. Commonly used drugs include melphalan, prednisone, chlorambucil, cyclophosphamide, and colchicine, but the results are generally unsatisfactory.
  Recent reports suggest that high-dose melphalan followed by bone marrow or stem cell transplantation shows promising therapeutic potential.

• Treatment for secondary amyloidosis focuses on the underlying condition, such as controlling chronic inflammation, infections, or tumors.

Does renal amyloidosis require hospitalization?

Yes.

Can renal amyloidosis be cured?

No.

DIET & LIFESTYLE

What should patients with renal amyloidosis pay attention to in their diet?

• It is advisable to consume easily digestible high-calorie foods and foods rich in vitamins and minerals;

• Avoid greasy, raw, cold, and irritating foods.

• Patients with renal insufficiency should limit protein intake. Patients with nephrotic syndrome should restrict salt, use diuretics, and receive human albumin infusions. Patients with cardiac insufficiency should limit water intake and follow a low-salt, low-fat diet.

What should patients with renal amyloidosis pay attention to in daily life?

• Get adequate rest;
• Avoid fatigue and infections;
• Maintain a calm mindset;
• Follow a low-salt, low-fat diet;
• Closely monitor fluid intake and output.

Do patients with renal amyloidosis need follow-up examinations? How are follow-up examinations conducted?

Yes, follow the doctor's instructions for regular blood, urine, imaging, and other relevant tests.

PREVENTION

Can renal amyloidosis be prevented? How to prevent renal amyloidosis?

The exact cause of this disease is currently unclear, and there are no proven effective preventive measures. For secondary renal amyloidosis, the primary disease should be actively treated.

How can patients with renal amyloidosis prevent complications?

Early diagnosis and early treatment can improve prognosis, reduce complications, and increase survival rates.