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A summary of the diagnostic strategy model is presented in TABLE 79.1.
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Probability diagnosis
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Excluding planned dietary restriction, psychological factors are the most common cause, particularly recent stress and anxiety.1 Elderly people with adverse psychological factors, neglect and possibly drug effects can present with wasting.
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Serious disorders not to be missed
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Many of the problems causing weight loss are very serious, especially malignant disease.
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Weight loss may be a manifestation of any malignancy. With cancer of the stomach, pancreas and caecum, malignant lymphomas and myeloma, weight loss may be the only symptom. Occult malignancy must be regarded as the most common cause of weight loss in the absence of major symptoms and signs. The mechanisms may be multiple, with anorexia and increased metabolism being important factors.
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These are now less common but tuberculosis must be considered, especially in people from less developed countries. Some cases of infective endocarditis may progress only very slowly with general debility, weight loss and fever as major features.2
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Other infections to consider are brucellosis, and protozoal and systemic fungal infection. Infection with HIV virus must be considered, especially in high-risk groups.
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Drug dependency, including alcohol and narcotic drugs, must be considered, especially when the problem may result in inappropriate nutrition. Apart from malignant disease there is a whole variety of gastrointestinal disorders that require consideration—these include malabsorption states, gastric ulceration, and intestinal infestations, especially in people returning from a significant stay in tropical and under-developed countries.
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Addison disease (CHAPTER 23) can be very difficult to diagnose. Symptoms include excessive fatigue, anorexia, nausea and postural dizziness. Hyperpigmentation is a late sign.
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Seven masquerades checklist
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Depression and the endocrine disorders, diabetes mellitus and hyperthyroidism, are important causes.
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The diabetic who presents with weight loss will be young and insulin-dependent. The initial presentation may be ketoacidosis. The triad of symptoms is thirst + polyuria + weight loss.
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This is usually associated with weight loss although in some, such as an elderly male, it may not be obvious. An important clue will be weight loss in the presence of an excellent appetite and this helps to distinguish it from a psychoneurotic disturbance.
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Weight loss is a common feature of depression and is usually proportional to the severity of the disease. In the early stages of depression, weight gain may be present but when the classic loss of the four basic drives (appetite, energy, sleep and sex) becomes manifest, weight loss is a feature.
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Any prescribed drugs causing anorexia can cause weight loss. Important drugs include digoxin, narcotics, cytotoxics, NSAIDs, some antihypertensives and theophylline. Be mindful of inappropriate use of thyroxine and laxatives.
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Red flag pointers for weight loss
Weight loss per se is a big red flag
Rapid weight loss with malaise
Acid dental erosion on surfaces of upper teeth: think bulimia
Weakness and malaise in young females: consider eating disorder and hypokalaemia
Evidence of abuse in a child
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Psychogenic considerations
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Weight loss is a feature of anxiety as well as depression. Some patients with psychotic disturbances, including schizophrenia and mania, may present with weight loss.
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Anorexia nervosa is quite common and is almost entirely confined to females between the ages of 12 and 20 years. The main differential diagnosis is hypopituitarism, although anorexia nervosa can cause endocrine disturbances through the hypothalamic pituitary axis.