Light chain amyloidosis or AL amyloidosis is the most common of the different types of amyloidosis. It used to be called primary amyloidosis. About 5 to 12 cases per million occur per year.
Definition & Facts
In AL amyloidosis, the plasma cells produce bits of proteins called amyloids that fold over in a way that make them insoluble. They then clump up to make fibrils that travel to other organs in the body and damage them.
They have a characteristic green glow when they are stained and looked at under polarized light. They can infiltrate any organ except the brain, but the most common injuries occur in the kidney, the liver, the heart, and the nervous system.
Symptoms & Complaints
As a result of its effect on the autonomic nervous system, AL amyloidosis can cause hypotension, or dangerously low blood pressure. It can also cause erectile dysfunction and interfere with the motility of the intestines.
People with AL amyloidosis don’t eat as much as they should because the disease causes the stomach to empty much more slowly than normal, which makes the person feel full. This symptom can become so severe that the person needs to be fed intravenously.
The person can also develop carpal tunnel syndrome, nodules under their skin, and arthropathy, which is any sort of disease that affects the joints. They can lose their hair and have unhealthy nails. The glands beneath their jaw can become enlarged. Amyloidosis can cause laryngitis and vocal hoarseness.
Another symptom of AL amyloidosis is periorbital purpura. This is bleeding beneath the skin around the eyes, which is exacerbated by coughing, sneezing, or laughing. It’s also called panda or raccoon eyes. Bleeds in other areas of the body are also common. Though it’s not as common, AL amyloidosis can cause an underactive thyroid (hypothyroidism) or underactive adrenal gland.
Researchers are not sure what causes AL amyloidosis, but people who are most at risk are men who are 50 years or older who have comorbidities, including inflammatory diseases. AL amyloidosis can occur spontaneously but is also associated with a type of white blood cell cancer called Waldenström's macroglobulinemia.
Diagnosis & Tests
Because AL amyloidosis is hard to diagnose, by the time it is diagnosed, the organ damage can be advanced. More and more, doctors are learning to suspect the disease if a patient comes in with cardiovascular disease, enlarged liver, or protein in their urine (proteinuria) that cannot be otherwise explained.
The first step in diagnosis is to find the amyloid and the abnormal plasma cells. Though the light chains that make up the fibrils can be found in the patient’s blood and the urine, a fine-needle aspiration of the patient’s abdominal fat can find the amyloid deposits. If the fat from the abdomen doesn’t help with the diagnosis, deposits can be found in the gums, the salivary glands, the rectum and the skin. The doctor may still have to biopsy an organ to get a definitive diagnosis.
After the amyloid proteins are found, the doctor then needs to find the abnormal plasma cells. This is done through a bone marrow biopsy.
Other tests to find AL amyloidosis are the serum free light-chain measurement or FLC. The FLC sometimes not only diagnoses the disease itself but also tells the doctor how far it has progressed and how it is responding to treatment.
Another diagnostic techniques is bone scintigraphy. A bone scan is a type of scintigraphy. Radioisotopes are introduced into the body to produce a two dimension picture of an organ or system. The radioisotope usually used is technetium TC99 M pyrophosphate. This type of isotope works very well in the heart, though an echocardiogram works even better. Scintigraphy usually only works on patients whose disease is advanced.
Doctors use biomarkers such as peptides or troponins to diagnose AL amyloidosis. Peptides are chains of amino acids, while troponins are proteins found in the cardiac muscle.
Treatment & Therapy
The aim of treatment is to reduce the number of amyloids and abnormal plasma cells in the bone marrow to the point where the patient has a noticeable improvement in their quality of life and in the functioning of their organs. When this happens, the patient can see improvement in their organ function and quality of life over three to six months, though sometimes improvement can take years. Current treatment modalities can be uncertain, though scientists are always working on improved treatment techniques for AL amyloidosis.
Many patients respond to restrictions in their sodium intake and diuretics, even though the diuretics need to be closely monitored. They are also given angiotensin-converting enzyme inhibitors, but these must be used carefully to guard against dangerous hypotension. The food intake of the patient must also be increased. Dialysis is given to patients whose AL amyloidosis has led to end stage renal disease, or ESRD.
Another treatment for patients who can tolerate it is peripheral blood stem cell transplantation preceded by high doses of melphalan, a chemotherapy drug. The downside of this treatment is that it is toxic, especially to people whose organs are already badly damaged. In some cases, it is even dangerous for the stem cells to be collected from the patient. Because of this, some patients receive stem cells from other sources. Others even receive doses of chemotherapy drugs before they start on the melphalan. The doctor needs to be sure that their patient is a good candidate for this therapy.
Another way to treat AL amyloidosis is to give the patient low doses of melphalan with prednisone, though this too has risks. Prednisone is a steroid and can cause water retention, which many patients can’t tolerate.
Prevention & Prophylaxis