Primary myelofibrosis can begin with a blood picture similar to that found in polycythemia vera or chronic myeloid leukemia. Most people with myelofibrosis have moderate to severe anemia. Eventually thrombocytopenia, a decrease of blood platelets develops. When viewed through a microscope, a blood smear will appear markedly abnormal, with presentation of pancytopenia, which is a reduction in the number of all blood cell types: red blood cells, white blood cells, and platelets. Red blood cells may show abnormalities including bizarre shapes, such as teardrop-shaped cells, and nucleated red blood cell precursors may appear in the blood smear (leukoerythroblastic reaction). Normally, mature red blood cells in adults do not have a cell nucleus, and the presence of nucleated red blood cells suggests that immature cells are being released into the bloodstream in response to a very high demand for the bone marrow to produce new red blood cells. Immature white cells and platelets (large megakaryocytes) are also seen in blood samples, and basophil counts are increased. When late in the disease progression an attempt is made to take a sample of bone marrow by aspiration, it may result in a dry tap, meaning that where the needle can normally suck out a sample of semi-liquid bone marrow, it produces no sample because the marrow has been replaced with collagen fibers. A bone marrow biopsy will reveal collagen fibrosis, replacing the marrow that would normally occupy the space. Treatment
The one known curative treatment is allogeneic stem cell transplantation, but this approach involves significant risks.
Bethanechol is a parasympathomimetic choline carbamate that selectively stimulates muscarinic receptors without any effect on nicotinic receptors. Unlike acetylcholine, bethanechol is not hydrolyzed by cholinesterase and will therefore have a long duration of action. Bethanechol is sold under the brand names Duvoid (Roberts), Myotonachol (Glenwood), Urecholine (Merck Frosst) and Urocarb (Hamilton). The name bethanechol refers to its structure as the urethane of beta-methylcholine. Medical uses
Bethanechol alleviates dry mouth and is sometimes given orally or subcutaneously to treat urinary retention resulting from general anesthetic, diabetic neuropathy of the bladder, or a side effect of antidepressants; or to treat gastrointestinal lack of muscular tone. The muscarinic receptors in the bladder and gastrointestinal tract stimulate contraction of the bladder and expulsion of urine, and increased gastrointestinal motility, respectively. Bethanechol should be used to treat these disorders only after mechanical obstruction is ruled out as a possible cause. Its potential benefit in the treatment of cerebral palsy has been investigated.Atropine is given preoperatively to prevent voiding of the bowel/bladder during surgery, Bethanechol is then given postoperatively to revert this action. Contraindications
Use of bethanechol, as well as all other muscarinic receptor agonists, is contraindicated in patients with asthma, coronary insufficiency, peptic ulcers, intestinal obstruction and hyperthyroidism. The parasympathomimetic action of this drug will exacerbate the symptoms of these disorders. References
External links
"Bethanechol". Drug Information Portal. U.S. National Library of Medicine.