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Selenium is an essential trace element that is known to be a component of glutathione peroxidase, a scavenger of hydroperoxides.1 Its deficiency causes a decrease in glutathione peroxidase function, thereby resulting in oxidative damage to many organs. The two major clinical signs in patients with selenium deficiency are skeletal myopathy and cardiomyopathy. White muscle disease, named because of its characteristic acolouration of the muscle is a myopathy caused by selenium deficiency in animals in the areas where the soil is low in selenium.2 In humans, it was demonstrated that Keshan disease, dilated cardiomyopathy in the Keshan area in China, was caused by selenium deficiency.3 In addition, there are reports that selenium deficiency occurs in patients who are nourished by total parenteral nutrition alone for a long time because of inflammatory bowel disease or resection of the intestine due to various intestinal diseases.4 5 We experienced a case of anorexia nervosa with skeletal myopathy caused by selenium deficiency under long term parenteral nutrition.
A 28 year old woman was admitted to our hospital with a 7 year history of anorexia nervosa receiving parenteral nutrition intermittently. At admission, she complained of general fatigue, but had no muscle weakness or myalgia. On physical examination, she was markedly emaciated (weight 22 kg, height 158 cm). Her skin was dry and her nail beds appeared pale. Because her voluntary food intake was not sufficient to maintain an adequate weight, we started parenteral nutrition. A month after initiation of parenteral nutrition, her body weight had increased from 22 kg to 27 kg and her presenting complaint of general fatigue had disappeared. Instead, she had begun to complain of proximal muscle pain and weakness in all four limbs, and soon after, she had difficulty in walking or standing up.
Laboratory studies showed a rapid rise in creatine kinase to 5638 (normal 35–169) IU/l. Other myogenic enzymes such as myoglobin and aldolase were also raised. Serum electrolytes were all within the normal range. Serum thyroxin and thyroid stimulating hormone concentrations were normal, but serum triiodothyronine was slightly decreased because of impaired conversion of thyroxin caused by malnutrition. Serum selenium concentration markedly decreased to 13 (normal 107–171) μg/l, and glutathione peroxidase also decreased to 145 (normal 280–450) IU/l. Serum vitamin E decreased to 0.35 (normal 0.75–1.41) mg/dl despite being added to the parenteral nutrition. Because serum vitamin E concentration often parallels the serum selenium concentration, these antioxidants will compensate for each other. The forearm ischaemic exercise test showed a normal response. Chest radioraphy showed neither congestive changes nor enlargement of the heart. On an echocardiogram, the wall motion of the left cardiac ventricle was normal. Electromyography of proximal limb muscles showed myopathic patterns. Motor and sensory nerve conduction velocities were normal.
The biopsied muscle from her left biceps seemed pale. Histological studies showed severe atrophy of all muscle fibres examined, type II fibre predominance, increased extramyofibrillar fluid without fibrosis, and many vacuoles in the myofibrils (figure A, B). The vacuoles were unstained by oil red O, periodic acid Shiff, or acid phosphatase, and were made up of subperimysial and intermyofibrillar clefts consisting of amorphous matrix material seen by electron microscopy. Myofibrillar architecture was destroyed and associated with loss and thinning of myofibrils. Some mitochondria were enlarged in size, but neither abnormal cristae nor inclusions were seen (figure C, D). These clefts and destroyed architecture of myofibrils would be caused by the intermyofibrillar and intramyofibrillar focal oedema that might be induced by unmetabolised hydroperoxides.
Within several days after a simple change from total parenteral nutrition to oral diet alone, without selenium supplementation, her muscle pain gradually improved. The serum creatine kinase concentration gradually decreased and was normal in a month. Two months later, she was able to walk alone and stand up from a chair. The concentrations of serum selenium and glutathione peroxidase tended to improve with oral diet alone.
Selenium is relatively abundant in meat, fish, and cereals, but there is very little in total parenteral nutrition or liquid formula diets. A patient nourished by total parenteral nutrition alone for a long period may risk selenium depletion, so selenium supplementation is recommended. In 1979 Van Rij et al reported a patient with a perforated small intestine showing skeletal myopathy during month long parenteral nutrition.4 Since then, there have been about 20 cases of selenium deficiency during total parenteral nutrition in the literature worldwide, but most cases received total parenteral nutrition because of the surgery for intestinal diseases or inflammatory bowel diseases. As far as we know, there is no report dealing with a patient with anorexia nervosa accompanied by selenium deficiency, although total parenteral nutrition is a popular method to ameliorate the nutritional state in severely emaciated patients with anorexia nervosa. The phenotypic difference for manifestation of either skeletal myopathy or cardiomyopathy is not understood at present. The living environment, the selenium content of the whole body, and the level of other antioxidants such as vitamin E, seem to influence one another.
Sudden death occurs occasionally in patients with anorexia nervosa because of arrhythmia and heart failure. Because selenium deficiency can cause cardiomyopathy and sudden death, we should carefully monitor for selenium deficiency in anorexia nervosa, especially in patients on long term total parenteral nutrition.
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