Primary Biliary Cirrhosis (cont.)
John M. Vierling, MD, FACP
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.
Leslie J. Schoenfield, MD, PhD
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.
In this Article
- What is PBC?
- What is the scope of the problem?
- What is the cause of PBC?
- What are the symptoms and physical findings in PBC?
- What manifestations are specifically due to PBC itself?
- What are the manifestations of the complications of cirrhosis in PBC?
- What are the manifestations of diseases associated with PBC?
- What are risk factors for PBC?
- How is PBC diagnosed?
- What is the role of blood tests?
- What is the role of testing for antimitochondrial antibodies?
- What is the role of imaging tests?
- What is the role of liver biopsy?
- What are the criteria for a definitive diagnosis of PBC
- What is the course of natural progression in PBC?
- What are the sequential clinical phases of PBC?
- What is the role of mathematical models in predicting the outcome (prognosis) in PBC?
- What about pregnancy in PBC?
- Find a local Gastroenterologist in your town
Metabolic Bone Disease
Patients with PBC may experience pain in the bones of their legs, pelvis, back (spine), or hips. This bone pain can come from one of two bone diseases, osteoporosis (sometimes referred to as thin bones) or osteomalacia (soft bones). Patients with PBC have a 440% increase in the likelihood of having poorly calcified bones compared to normal people of the same age and gender. Most people with osteoporosis or osteomalacia, however, do not have bone pain. Still, a minority do experience bone pain that can be severe, often due to bone fractures.
Poorly calcified bones (osteopenia) characterize both osteoporosis and osteomalacia. The cause of the osteopenia in osteoporosis, however, is not known, although the development of osteoporosis tends to speed up in women after the onset of menopause. In osteoporosis, there is chronic, accelerated loss of calcium and protein from the bones. By contrast, in osteomalacia, the osteopenia results from failure of the bones to calcify. The cause of osteomalacia is vitamin D deficiency.
While the body's processing (metabolism) of dietary calcium and vitamin D is normal in PBC, bone metabolism is abnormal. Normal bone metabolism involves an ongoing balance among production of new bone, calcification of bone, and loss of bone. Vitamin D plays a key role in regulating the deposition of calcium in bone. What then, causes the deficiency of vitamin D in PBC? First of all, patients with PBC and advanced cholestasis, usually recognized by significant jaundice, can have a decreased ability to absorb dietary vitamin D from the gut. (Please see the section on fat malabsorption and jaundice.) Additionally, poor pancreatic function, celiac sprue, and scleroderma with bacterial overgrowth may be present in some patients with PBC. Each of these conditions can further impair the ability to absorb dietary vitamin D from the intestines.
The resulting vitamin D deficiency is the cause of the decreased deposit of calcium in the bones in osteomalacia. All of this said, compared to osteoporosis, osteomalacia is rare, especially among patients who are exposed to sunlight throughout the year. That's because sunlight stimulates the production of vitamin D in the skin, which can compensate for the poor absorption of vitamin D from the diet.
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