John M. Vierling M.D. is Professor of Medicine and Surgery at the Baylor College of Medicine in Houston, Texas, where he also serves as Director of Baylor Liver Health and Chief of Hepatology. In addition, he is the Director of Advanced Liver Therapies, a center devoted to clinical research in hepatobiliary diseases at St. Luke's Episcopal Hospital. Dr. Vierling is board certified in internal medicine and gastroenterology and a Fellow of the American College of Physicians.
Dr. Schoenfield served as associate professor of medicine and consultant in gastroenterology on the faculty of the Mayo Clinic for seven years. He became a professor of medicine in residence at UCLA from 1972 to 1999 (now emeritus). He was the director of gastroenterology at Cedars-Sinai Medical Center in Los Angeles for 25 years, where he received the chief resident's teaching award, the president's award, and the pioneer of medicine award.
The cause of PBC remains unclear. Current information suggests the cause may
involve autoimmunity, infection, or genetic (hereditary) predisposition, acting
either alone or in some combination. A complete understanding of the cause of
PBC will require two types of information. One, referred to as the etiology, is
identification of the initiating (triggering) events. The other, referred to as
the pathogenesis, is a discovery of the ways (mechanisms) by which the
triggering events lead to the inflammatory destruction of bile ducts and
hepatocytes. Unfortunately, neither the etiology nor the pathogenesis of PBC has
yet been defined.
PBC is presumed by most experts to be an autoimmune disease, which is an
illness that occurs when the body's tissues are attacked by its own immune
(defense) system. (Auto means self.) Childhood diabetes is one example of an
autoimmune disease in which some type of transient infection (one that later
goes away) triggers an immune reaction in a susceptible (genetically
predisposed) person. This particular immune reaction in diabetes selectively
destroys the cells in the pancreas that produce insulin.
Despite strong evidence to support the concept that PBC likewise is an
autoimmune disease, some features of PBC are uncharacteristic of autoimmunity. For example, all other autoimmune diseases occur in both children and
adults, while, as already mentioned, PBC has never been diagnosed in childhood.
PBC and other autoimmune diseases, however, are associated with antibodies
(small proteins found in the blood and bodily secretions) that react with the
body's own proteins, which are referred to as autoantigens.
Table 1 shows a comparison between primary biliary cirrhosis and classic autoimmune
diseases.
Feature
Primary Biliary Cirrhosis
Classic Autoimmunity
Predominantly females
Yes
Yes
Age at diagnosis
Adults only
Children and adults
Autoantibodies
Yes
Yes
Antigens recognized by autoantibodies
Restricted (few)
Diverse (many)
HLA (Human Lymphocyte Antigen) associations
Weak
Strong
Association with other autoimmune diseases
Yes
Yes
Response to drugs that suppress the immune system
Poor
Good
Specific types of white blood cells called B-lymphocytes make antibodies.
Antibodies recognize specific protein targets called antigens (substances that
are capable of causing the production of antibodies.) To facilitate our
discussion of autoimmunity, let us first look at what happens in the more common
type of immunity. It takes new or foreign antigens to produce this usual type of
immunity. Vaccines, infectious organisms (like viruses or bacteria), or
surgically transplanted tissues contain such foreign antigens. So, for instance,
when a person is first vaccinated to prevent tetanus, that person is newly
exposed to tetanus proteins, which are foreign antigens. What happens then?
First, specialized cells within tissues of the body take up and digest the
tetanus proteins. Then the protein fragments are attached to special molecules
called HLA molecules that are produced by the HLA complex. (HLA is an
abbreviation for Human Leukocyte Antigen). The HLA complex is a group of
inherited genes located on chromosome 6. The HLA molecules control a person's
immune response. Next, the protein (antigen) fragments bound to the HLA
molecules set into action (activate or stimulate) specialized white blood cells
called T-lymphocytes. The T-lymphocytes then begin to multiply (reproduce) and
secrete chemical signals into their environment.
Another type of white blood cell, called B-lymphocytes, also enters the
picture. B-lymphocytes have molecules on their surface, called immunoglobulins (Ig)
that can bind directly to undigested tetanus antigens. An essential part of the
body's immune system, immunoglobulins are antibodies that attach to foreign
substances, such as bacteria, and assist in destroying them. This binding
activates the B-lymphocytes, that is, gets them ready for action. Meanwhile, the
above-mentioned secreted chemicals of the activated T-lymphocytes provide a
helper signal for the B-lymphocytes. This signal tells the B-lymphocytes to
begin secreting the immunoglobulins (specific antibodies) that precisely
recognize the stimulating tetanus antigen.
The bottom line here is that antibodies that specifically bind and inactivate
tetanus proteins prevent an immunized person from developing tetanus. What is
more, both the T- and B-lymphocytes reside in the body as memory cells. This
means that they can remember to generate increased amounts of antibodies against
tetanus antigens whenever a person has a booster shot of the vaccine. So, that's
what happens in the common type of immunity.
By contrast, in autoimmunity, autoantibodies, produced by B-lymphocytes react
against self or auto antigens rather than against foreign antigens. In this
reaction, the activated B-lymphocytes still require help from chemicals secreted
by activated T-lymphocytes. Although the human immune system is capable of
recognizing a nearly infinite number of antigens, normally it does not recognize
or respond to autoantigens. The expected absence of immune responses against
self is called tolerance.
Thus, in all autoimmune diseases, including PBC, tolerance (absence of an immune response)
becomes defective (is lost) for autoantigens recognized by both T- and
B-lymphocytes. In other words, an immune response to autoantigens does occur. What's
more, in autoimmune diseases, B-lymphocytes initially produce autoantibodies
that recognize a single autoantigen. With time, however, B-lymphocytes produce
new autoantibodies that recognize additional autoantigens that are distinct from
the initial autoantigen. PBC, however, is the only allegedly autoimmune disease
in which this sequence does not occur. In other words, in PBC, the
autoantibodies recognize only the initial autoantigen.
Gallstones are stones that form when substances in the bile harden. Gallstones (formed in the gallbladder) can be as small as a grain of sand or as large as a golf ball. There can be just one large stone, hundreds of tiny stones, or any combination. The majority of gallstones do not cause symptoms.
Hypothyroidism is any state in which thyroid hormone production is below normal. Normally, the
rate of thyroid hormone production is controlled by the brain at the pituitary.
Hypothyroidism is a very common condition and the symptoms of hypothyroidism are
often subtle.
Liver cancer is the fifth most common cancer in the world and the majority of patients with liver cancer will die within one year as a result. Patients with associated cirrhosis caused by chronic hepatitis B or C infections, alcohol, and hemochromatosis are at the greatest risk of developing liver cancer. Many patients with liver cancer do not develop symptoms until the advanced stages of the tumor which usually makes prognosis poor. The combination of an imaging study (ultrasound, CT, or MRI scans) and an elevated blood level of alpha-fetoprotein will most effectively diagnose liver cancer, while a liver biopsy can make a definitive diagnosis. Medical treatments, including chemotherapy, chemoembolization, ablation, and proton beam therapy, are not very effective. Surgical removal of the tumor or a liver transplant may be most effective in certain cases.
Cirrhosis of the liver refers to a disease in which normal liver cells are replaced by scar tissue caused by alcohol and viral hepatitis B and C. This disease leads to abnormalities in the liver's ability to handle toxins and blood flow, causing internal bleeding, kidney failure, mental confusion, coma, body fluid accumulation, and frequent infections. Symptoms include yellowing of the skin, itching, and fatigue.
Sjögren's syndrome is an autoimmune disease involving the abnormal production of extra antibodies that attack the glands and connective tissue. Sjögren's syndrome with gland inflammation (resulting dry eyes and mouth, etc.) that is not associated with another connective tissue disease is referred to as primary Sjögren's syndrome. Sjögren's syndrome that is also associated with a connective tissue disease, such as rheumatoid arthritis, systemic lupus erythematosus, or scleroderma, is referred to as secondary Sjögren's syndrome. Though there is no cure for Sjögren's syndrome, the symptoms may be treated by using lubricating eye ointments, drinking plenty of water, humidifying the air, and using glycerin swabs. Medications are also available to treat dry eye and dry mouth.
Edema is the swelling of tissues as a result of excess water accumulations. Peripheral edema occurs in the feet and legs. There are two types of edema, non-pitting edema and pitting edema. Causes of pitting edema is caused by systemic diseases, most commonly involving the heart, liver, and kidneys. Local conditions that cause edema are thrombophlebitis and varicose veins. Edema is generally treated with medication.
Itching can be a common problem. Itches can be localized or generalized. There are many causes of itching to include: infection (jock itch, vaginal itch), disease (hyperthyroidism, liver or kidney), reactions to drugs, and skin infestations (pubic or body lice). Treatment for itching varies depending on the cause of the itch.
Jaundice is a yellowish staining of the skin and whites of the eyes (sclerae) with bilirubin, the pigment found in bile. Jaundice can be an indicator of liver or gallbladder disease, or it may result from the rupture of red blood cells (hemolysis).
Ulcerative colitis is a chronic inflammation of the colon. Symptoms include abdominal pain, diarrhea, and rectal bleeding. Ulcerative colitis is closely related to Crohn's disease, and together they are referred to as inflammatory bowel disease. Treatment depends upon the type of ulcerative colitis diagnosed.
Learn about osteoporosis, a condition characterized by the loss of bone density, which leads to an increased risk of bone fracture. Unless one experiences a fracture, a person may have osteoporosis for decades without knowing it. Treatment for osteoporosis may involve medications that stop bone loss and increase bone strength and bone formation, as well as quitting smoking, regular exercise, cutting back on alcohol intake, and eating a calcium- and vitamin D-rich balanced diet.
Scleroderma is an autoimmune disease of the connective tissue. It is characterized by the formation of scar tissue (fibrosis) in the skin and organs of the body, leading to thickness and firmness of involved areas. Scleroderma is also referred to as systemic sclerosis, and the cause is unknown. Treatment of scleroderma is directed toward the individual features that are most troubling to the patient.
The liver is the largest solid organ in the body, and is actually an gland. The liver has a wide variety of critical functions such as manufacturing proteins and metabolizing fats and carbohydrates. The liver also eliminates harmful biochemical waste products from the body (alcohol, drugs, toxins). The liver secretes bile that aids in digestion. Examples of diseases of the liver include cirrhosis, hepatitis, cancer, and fatty liver. Symptoms of liver disease include bleeding, easy bruising, edema, fatigue, and jaundice.
Digestion is the complex process of turning food you eat into the energy you need to survive. The digestive process also involves creating waste to be eliminated, and is made of a series of muscles that coordinate the movement of food.
Thyroiditis is the inflammation of the thyroid gland. The inflamed thyroid gland can release an excess of thyroid hormones into the blood stream, resulting in a temporary hyperthyroid state. Some forms of thyroiditis can be diagnosed based on tenderness and enlargement of the thyroid gland. A thyroid scan sometimes is used in making the diagnosis. Thyroiditis can also be diagnosed with a biopsy of the thyroid gland.
Digestion RSS
Healthy Living Tips
This site complies with the