I HAVE A PATIENT WITH FATIGUE
How do I determine the cause?
Mrs. M is a 42-year-old woman who has had fatigue for the past 6 months.
What is the differential diagnosis of fatigue? How would you frame the differential?
CONSTRUCTING A DIFFERENTIAL DIAGNOSIS
Before considering the differential diagnosis, it is important to understand what the patient means by fatigue, which is conventionally defined as a sensation of exhaustion after usual activities, or a feeling of insufficient energy to begin usual activities. Most people consider the terms fatigue, tiredness, and lack of energy synonymous. However, patients sometimes use these terms when they are actually experiencing other symptoms, especially excessive sleepiness, weakness, or dyspnea on exertion.
Always ask patients what they mean when they report fatigue. Always ask directly about weakness, excessive sleepiness, and dyspnea.
Acute fatigue is common in conjunction with a variety of acute illnesses, ranging from uncomplicated viral infections to exacerbations of heart failure (HF). Fatigue is also a prominent symptom in some chronic diseases, such as multiple sclerosis and cancer. This chapter will not discuss fatigue in such patients but will focus on evaluating the symptom of fatigue lasting weeks to months in patients without already diagnosed conditions known to cause fatigue.
The differential diagnosis of fatigue is extremely broad and best organized with an organ/system approach.
Obstructive sleep apnea (OSA)
Periodic leg movements
Medications (Table 18-1)
Hematologic or oncologic
Renal: chronic kidney disease
Cardiovascular: chronic heart disease
Pulmonary: chronic lung disease
Neuromuscular: myositis, multiple sclerosis
Infectious: chronic infections
Rheumatologic: autoimmune diseases
Fatigue of unknown etiology
Chronic fatigue syndrome
Idiopathic chronic fatigue: fatigue for which no medical, psychiatric, or sleep pattern explanation can be found.
Table 18-1.Medications that affect sleep. |Favorite Table|Download (.pdf) Table 18-1. Medications that affect sleep.
|Medications that cause insomnia ||Antidepressants: Bupropion, venlafaxine, fluoxetine, sertraline |
|Anticholinergics: Ipratropium |
|CNS stimulants: Methylphenidate, modafinil |
|Hormones: Oral contraceptives, thyroid hormone, corticosteroids, progesterone |
|Sympathomimetic amines: Albuterol, theophylline, phenylpropanolamine, pseudoephedrine |
|Antineoplastics: Leuprolide, goserelin, pentostatin, interferon alfa |
|Miscellaneous: Phenytoin, nicotine, levodopa, quinidine, caffeine, alcohol |
|Medications that cause drowsiness ||Tricyclic antidepressants: Amitriptyline, imipramine, nortriptyline |
|Other antidepressants: Mirtazapine, trazodone, paroxetine |
|Nonsteroidal anti-inflammatory drugs |
|Neuropathic pain agents: Gabapentin, pregabalin |
|Antihistamines: Diphenhydramine, hydroxyzine, meclizine |
|Atypical antipsychotics |
Figure 18-1 outlines the diagnostic approach to fatigue.
Diagnostic approach: fatigue.
The most common causes of fatigue are psychiatric disorders, sleep disorders, and medication side effects.
Mrs. M reports that she is tired all the time, beginning first ...