special subjects
Fatigue
Introduction
Fatigue is difficulty initiating and sustaining activity due to a lack of energy and accompanied by a desire to rest. Fatigue is normal after physical exertion, prolonged stress, and sleep deprivation. Fatigue occurs most often as part of a symptom complex, but even when it is the sole or main presenting symptom, fatigue is one of the most common symptoms. Patients may refer to certain other symptoms as fatigue; differentiating between them and fatigue is usually, but not always, possible with detailed questioning. Weakness , a symptom of nervous system or muscle disorders, is insufficient force of muscular contraction at maximum effort. Disorders such as Dyspnea on exertion, an early symptom of cardiac and pulmonary disorders, can decrease exercise tolerance, simulating fatigue. Respiratory symptoms usually can be elicited upon careful questioning or develop subsequently. Somnolence, a symptom of disorders causing sleep deprivation (eg, Allergic Rhinitis , Fatigue can be classified in various temporal categories, such as the following: Recent fatigue: < 1 month duration Prolonged fatigue: 1 to 6 months duration Chronic fatigue: > 6 months duration Chronic Fatigue Syndrome is one cause of chronic fatigue. There are now 2 other terms for chronic fatigue syndrome—myalgic encephalomyelitis and systemic exertion intolerance—although there is no clear delineation between these at this time. Patients with 