Differential Diagnosis for Fatigue

The differential diagnosis for fatigue is extensive and can be categorized into several groups. Here's a breakdown of potential causes, organized by their likelihood and potential impact:

• Single Most Likely Diagnosis

  • Depression: Fatigue is a common symptom of depression, and given its prevalence, it's often one of the first considerations. Depression can cause significant changes in motivation, energy levels, and interest in activities.
  • Anemia: Especially iron-deficiency anemia, which is common and can cause fatigue due to a decrease in the number of red blood cells or the amount of hemoglobin in the blood.

• Other Likely Diagnoses

  • Hypothyroidism: A condition where the thyroid gland doesn't produce enough thyroid hormone, leading to fatigue, among other symptoms.
  • Diabetes: Both type 1 and type 2 diabetes can cause fatigue due to high blood sugar levels, which can lead to feelings of tiredness.
  • Sleep Apnea: A condition that affects breathing during sleep, leading to poor sleep quality and subsequent fatigue.
  • Chronic Fatigue Syndrome (CFS)/Myalgic Encephalomyelitis (ME): A long-term illness characterized by extreme fatigue that cannot be explained by any underlying medical condition.
  • Medication Side Effects: Many medications can cause fatigue as a side effect, including sedatives, antidepressants, and antihistamines.

• Do Not Miss Diagnoses

  • Addison's Disease: A rare disorder of the adrenal glands where not enough cortisol and aldosterone are produced, leading to fatigue among other severe symptoms.
  • Heart Failure: Fatigue can be an early symptom of heart failure, where the heart is unable to pump enough blood to meet the body's needs.
  • Chronic Kidney Disease: Especially in its advanced stages, can cause fatigue due to the buildup of toxins in the blood.
  • HIV/AIDS: Fatigue is a common symptom in the early stages of HIV infection and can also occur in later stages due to the disease itself or the side effects of antiretroviral therapy.
  • Cancer: Certain types of cancer, such as leukemia or lymphoma, can cause fatigue as an early symptom.

• Rare Diagnoses

  • Mitochondrial Myopathies: A group of disorders caused by defects in the mitochondria, which can lead to fatigue and muscle weakness.
  • Pernicious Anemia: A rare vitamin B12 deficiency caused by a lack of intrinsic factor in the stomach, leading to fatigue and other neurological symptoms.
  • Wilson's Disease: A genetic disorder that leads to copper accumulation in the body, causing fatigue, liver disease, and neurological symptoms.
  • Porphyrias: A group of rare genetic disorders that can cause fatigue, among other symptoms like abdominal pain and neurological issues.

Each of these diagnoses has a unique set of accompanying symptoms and diagnostic criteria. A thorough medical history, physical examination, and appropriate laboratory tests are essential for determining the underlying cause of fatigue.