A 40-year-old woman comes to the physician reporting she has pain in her entire body. She says that for a period of several years she has had pain and stiffness that predominantly affects her shoulders, upper back, hips, thighs and knees. She also reports that she has fatigue and an increased need for sleep, sometimes sleeping for 14 hours per day but it is of low quality. She also has cognitive slowing and feels that she is “not all there mentally”. Her pulse is 68/mm, blood pressure is 140/58mmHg, respirations are 14/mm and temperature is 37.2C (98.9’F). She has pain to palpation of her deltoids, trapezius, lattisimus dorsi and her quadriceps. She has no joint deformities nor joint swelling or redness. Which of the following is the most likely diagnosis?

**Core Concept**
Fibromyalgia is a chronic condition characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, and cognitive impairment. It is a complex disorder that affects multiple systems, including the nervous, musculoskeletal, and endocrine systems.

**Why the Correct Answer is Right**
The patient's symptoms, including widespread pain, fatigue, sleep disturbances, and cognitive impairment, are classic for fibromyalgia. The absence of joint deformities, swelling, or redness suggests that the pain is not due to an inflammatory or degenerative joint disease. Fibromyalgia is often associated with tender points, which are areas of muscle and tendon that are sensitive to pressure. The patient's pain to palpation of her deltoids, trapezius, latissimus dorsi, and quadriceps muscles is consistent with tender points. Additionally, fibromyalgia is often accompanied by other symptoms such as irritable bowel syndrome, migraines, and anxiety.

**Why Each Wrong Option is Incorrect**
**Option A:** Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disease that can cause widespread pain and fatigue, but it is typically accompanied by other symptoms such as skin rashes, joint swelling, and kidney involvement. This patient's lack of these symptoms makes SLE less likely.
**Option B:** Rheumatoid Arthritis (RA) is a chronic autoimmune disease that causes joint inflammation and deformity. This patient's lack of joint deformity and swelling makes RA less likely.
**Option C:** Hypothyroidism can cause fatigue, sleep disturbances, and cognitive impairment, but it is typically accompanied by other symptoms such as weight gain, hair loss, and cold intolerance. This patient's lack of these symptoms makes hypothyroidism less likely.

**Clinical Pearl / High-Yield Fact**
Fibromyalgia is often associated with other conditions such as irritable bowel syndrome, migraines, and anxiety. Patients with fibromyalgia may also have a higher prevalence of depression and sleep disorders. It is essential to consider these comorbidities when evaluating patients with fibromyalgia.

**Correct Answer: C. Hypothyroidism can cause fatigue, sleep disturbances, and cognitive impairment, but it is typically accompanied by other symptoms such as weight gain, hair loss, and cold intolerance. This patient's lack of these symptoms makes hypothyroidism less likely.

✓ Correct Answer: B. Fibromyalgia