Overview of amyloidosis
Amyloidosis is a group of clinical syndromes with multiple causes. It is not a clinically independent disease, but rather a group of tissue-induced protein deposition disorders. The disease was first discovered by Wirchow in 1854, and the diagnostic rate has increased significantly over the past 20 years as amyloidogenic substances have been extracted from the tissues of patients with a variety of disorders and their corresponding chemical compositions have been further analyzed. In fact, amyloidosis is not clinically uncommon. It is characterized by the deposition of amyloid substances in the walls of blood vessels and tissues, causing a variety of pathologies, mainly involving the heart, kidneys, liver, spleen, gastrointestinal tract, joints, muscles and skin organs and tissues. Deposits can occur locally or systemically, and the course of the disease can be benign or malignant. When amyloidosis involves the joints, it can cause amyloidosis-related osteoarthropathy.
Causes
The etiology of this disease is unclear, but various cytokines, growth factors and related inflammatory mediators may play a role.
Secondary amyloidosis-related arthropathy is common in the following conditions:
1. chronic infections: tuberculosis, osteomyelitis, schistosomiasis, etc.
2. Rheumatic diseases: ankylosing spondylitis, systemic lupus erythematosus, leukemia, etc.
3. Malignant tumors: lymphosarcoma, esophageal cancer, cervical cancer, etc.
4. Others: narcotic addiction, periodic granulocytopenia, etc.
The etiology of senile amyloidosis is not clear at present.
Symptoms
Amyloid arthropathy: various types of amyloidosis can involve joints, especially AL and Aβ2M amyloidosis are easy to appear. AL amyloidosis mainly involves shoulder, wrist, knee and interphalangeal joints, etc., which can have morning stiffness, swelling of soft tissues around the joints, pressure and pain and limitation of activities, and it is sometimes very similar to rheumatoid arthritis. Subcutaneous nodules can be seen in the joints of more than half of the patients, and some patients may have carpal tunnel syndrome and/or “shoulder pad sign”. Amyloid can also be deposited in skeletal muscle, resulting in muscle hypertrophy or myopathy. Bone infiltrated by large amounts of amyloid can cause osteolytic lesions, leading to pathological fractures.The main manifestations of Aβ2M amyloidosis include carpal tunnel syndrome, joint effusion, limited joint movement, spondyloarthropathies, and cystic bone destruction. Osteoarthritis, calcium pyrophosphate deposition disease and intervertebral disc calcification can also be accompanied by joint amyloidosis.
Examination
1. Blood test and blood sedimentation
Secondary amyloidosis varies according to the primary disease, there may be mild anemia, elevated white blood cell count, rapid blood sedimentation, primary and familial type have no abnormal changes, secondary to plasma cell disease, the peripheral blood can be seen to have red blood cell crosstalk phenomenon.
2. Immunologic examination
Protein electrophoresis of blood and urine and quantitative determination of serum immunoglobulin, if special immunoglobulin is found, it is important for the diagnosis of AL amyloidosis.
3. X-ray examination
The disease often shows multiple symmetrical joint involvement, manifested as soft tissue mass in the joint area, and the bone near the joint end shows osteolytic changes. Due to ischemia of the bone and joint, the bone near the end of the joint can be limited necrosis, and the joint surface is flattened, and the bone is dense. When the hip is involved, the X-ray presentation resembles ischemic necrosis of the femoral head with clear margins. When the vertebral body develops, there may be extensive osteoporosis and cystic bone destruction, similar to myeloma.
4. Others
In addition, amyloid ultrastructural examination is also included.
Diagnosis
Pathologic histologic examination is the gold standard for diagnosis of the disease and the only way to confirm the diagnosis. Obtaining enough suitable specimens is the key to histologic examination. The sites of biopsy are mainly abdominal subcutaneous fat, bone marrow, and rectal mucosa.
Immunohistochemistry and ultrastructural examination of immunolabeling under the electron microscope can help classify the disease.
Treatment
1. Specific treatment
(1) AL amyloidosis: either combination chemotherapy with oxfenarsine (Marfan) and prednisone (MP regimen) or iododeoxyadriamycin can be applied.
(2) AA amyloidosis: treat the underlying disease with colchicine or cytotoxic drugs.
2. Symptomatic, supportive and alternative treatments
Amyloidosis-associated osteoarthropathy requires symptomatic, supportive and alternative treatment.
Prognosis
The prognosis of secondary amyloidosis depends on the success of the treatment of the primary disease, and amyloidosis-associated osteoarthropathy has a poor prognosis.