Which condition is characterized by chronic fatigue and weakness without an underlying medical cause?

Chronic fatigue syndrome, also known as myalgic encephalomyelitis, is a condition defined by persistent and unexplained fatigue that lasts for six months or more and is not the result of ongoing exertion or other medical conditions. This fatigue significantly interferes with daily activities and is often accompanied by additional symptoms such as sleep disturbances, cognitive impairment, and joint or muscle pain.

In this scenario, recognizing chronic fatigue syndrome is essential because it specifically aligns with the definition of chronic fatigue and weakness without an identifiable medical cause. Patients presenting with this syndrome often undergo extensive testing, ruling out other potential causes of their symptoms, which confirms that their fatigue is indeed unexplained by traditional diagnostic criteria.

The other options refer to different conditions that are associated with fatigue but also have distinct underlying causes or are part of a different symptom complex. Mononucleosis is often caused by the Epstein-Barr virus and typically has identifiable symptoms such as fever and sore throat. Neurasthenia involves a broader spectrum of physical and mental fatigue that may have various psychological and physiological stressors, while migraines are specific headache disorders that can cause fatigue but also present with additional symptoms like nausea or visual disturbances. Thus, chronic fatigue syndrome stands out as the most fitting option based on