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A specific causative medical disease (other than psychiatric disease and sleep disorders) that explains fatigue is found in less than 10% of patients who seek medical attention from their primary care physician. Up to 75% of patients with fatigue have psychiatric symptoms. Sleep disorders, especially OSA and insomnia syndromes, are also common in patients with fatigue, and in one referral clinic, 80% of patients with fatigue had sleep disorders. Because the differential diagnosis of fatigue is broad and difficult to limit during the initial assessment, it is necessary to explore for symptoms and signs of many possible etiologies in most patients, even those with pivotal psychiatric or sleep disorder symptoms. Patients with several somatic complaints, such as Mrs. M, are particularly likely to have psychiatric causes for fatigue, as are patients who feel tired constantly. Because sleep disorders are so common, either in association with psychiatric disorders or alone, they are always an active alternative in patients with fatigue. Patients often do not spontaneously describe sleep disturbances and psychiatric symptoms, so it is important to ask about them directly.
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All patients with fatigue need a detailed psychosocial and sleep history.
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Although most patients with fatigue do not have anemia, hypothyroidism, or diabetes mellitus, these conditions are important and treatable, and so are generally considered “must not miss” diagnoses. Anemia and hypothyroidism are somewhat likely in Mrs. M because of her previous history of anemia and her family history of thyroid disease. Finally, on occasion, fatigue may be the presenting symptom in patients with undiagnosed cardiac, pulmonary, renal, liver, rheumatologic, or chronic infectious disease. Table 18-2 lists the differential diagnosis.
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Despite the rarity of positive results, most patients with fatigue need basic laboratory testing consisting of a blood count, chemistry panel (including glucose, electrolytes, BUN, creatinine, calcium, and liver function tests), and a TSH.
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Mrs. M does not lack interest in her usual activities or feel depressed. She has not lost or gained weight. She worries about money and her family but has never had a panic attack and does not consider herself excessively nervous or anxious.
On physical exam, she appears healthy and her affect is normal. Her BMI is 35. HEENT exam is normal. There is no thyromegaly or adenopathy. Lungs are clear. There are no breast masses. Cardiac and abdominal exams are normal, and there is no edema. Her CBC, glucose, electrolytes, BUN, creatinine, liver function tests, and TSH are all normal.
Is the clinical information sufficient to make a diagnosis? If not, what other information do you need?
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Leading Hypotheses: Depression & Anxiety
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See Chapter 32, Unintentional Weight Loss.
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Mrs. M does not meet DSM criteria for anxiety or depression. It is therefore necessary to consider the alternative diagnoses.
Mrs. M works as a teacher, rising at 6 am, leaving her house at 7 am, and returning home about 5 pm. She then prepares dinner for her family, helps her 2 children with their homework, and grades papers until 9:30 pm. She watches a little television, and then goes to sleep about 10:00 pm. Her husband works from 3 pm to 11 pm, and she often wakes up when he gets home at midnight. He needs some time to “wind down” before he goes to sleep, so they often talk and watch TV in bed for an hour or so. After her husband dozes off, she often cannot fall back asleep, and will sit in bed “surfing” the Internet on her laptop for an hour or two. She also comments that she feels tired even when she sleeps straight through the night on the weekends, and her husband complains about her snoring.
Is the clinical information sufficient to make a diagnosis? If not, what other information do you need?
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Mrs. M’s sleep history clearly uncovers several sleep hygiene issues. However, she is also obese, a risk factor for OSA. Re-exploring her symptoms, it is notable that she has some morning headaches, feels fatigued even when she sleeps all night, and snores.