What syndrome is characterized by pain, stiffness, and extreme tenderness in muscles?

Fibromyalgia is characterized by widespread pain, stiffness, and extreme tenderness in muscles, making it distinct among the options presented. This condition often leads to additional symptoms such as fatigue, sleep disturbances, and cognitive difficulties, which are commonly referred to as "fibro fog." The hallmark of fibromyalgia is the presence of tender points across the body, where even slight pressure can cause significant pain.

The other mentioned conditions each have unique features that differentiate them from fibromyalgia. Chronic fatigue syndrome primarily presents with profound fatigue that doesn't improve with rest and is often accompanied by other symptoms like cognitive impairment. Myofascial pain syndrome is localized and associated with specific trigger points in muscles rather than diffuse tenderness. Rheumatoid arthritis predominantly affects the joints and is characterized by inflammatory pain and swelling, which does not align with the muscle-specific symptoms of fibromyalgia. Understanding these distinctions reinforces the unique characteristics associated with fibromyalgia as the correct answer.