Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 25-year-old woman is evaluated during a follow-up visit for a 6-month history of diffuse muscle and joint pain above and below the waist, fatigue, and difficulty sleeping. She has a 2-year history of hypothyroidism treated with levothyroxine. Her only other medication is hydrocodone-acetaminophen, which has not relieved her pain.
On physical examination, temperature is 37.0 °C (98.6 °F), blood pressure is 125/78 mm Hg, pulse rate is 85/min, and respiration rate is 12/min. Cardiopulmonary examination is normal. Musculoskeletal examination reveals diffuse periarticular tenderness, including bilateral tenderness in the biceps brachii, thighs, and calves. Muscle strength testing cannot be completed because of pain. The joints are not swollen, and she does not have lower-extremity edema.
Laboratory studies:
| Complete blood count | Normal |
| Complete metabolic panel | Normal |
| Erythrocyte sedimentation rate | 10 mm/h |
| Creatine kinase | 100 U/L |
| Antinuclear antibodies | Titer of 1:640 |
| Thyroid-stimulating hormone | 1.5 µU/mL (1.5 mU/L) |
| Urinalysis | Normal |
Which of following is the most likely diagnosis?
A) Fibromyalgia
B) Polymyositis
C) Sjögren syndrome
D) Systemic lupus erythematosus
MKSAP Answer and Critique
The correct answer is A) Fibromyalgia. This item is available to MKSAP 15 subscribers as item 30 in the Rheumatology section. More information about MKSAP 15 is available online.
This patient most likely has fibromyalgia. This condition is characterized by diffuse pain on both sides of the body and above and below the waist as well as axial skeletal pain, or, according to the original American College of Rheumatology criteria, the presence of pain in at least 11 of 18 specified potential tender points. However, expert opinion now states that these tender points are arbitrary and not essential in the diagnosis of fibromyalgia.
Most patients with this condition have fatigue and sleep disturbance. Fibromyalgia also may be associated with dry eyes and mouth. Studies that have assessed the comorbidity of fibromyalgia with other symptom-defined syndromes have found high rates of chronic fatigue syndrome, migraine, irritable bowel syndrome, pelvic pain, and temporomandibular joint pain in patients with fibromyalgia.
Polymyositis may manifest as muscle pain and fatigue but is unlikely in the absence of significant proximal muscle weakness or an elevated creatine kinase level.
Up to 25% of patients with systemic inflammatory conditions, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis, have symptoms consistent with fibromyalgia in the initial stages of their illness. This patient’s fatigue, polyarthralgia, dry eyes and mouth, and strongly positive titers of antinuclear antibodies are consistent with SLE and Sjögren syndrome. However, patients with SLE usually have anemia, leukopenia, or lymphopenia. Similarly, joint involvement in Sjögren syndrome typically manifests as inflammatory arthritis. Furthermore, patients with SLE and Sjögren syndrome may have systemic manifestations, including cutaneous, neurologic, and renal involvement, which are absent in this patient.
The presence of antinuclear antibodies is not diagnostic of SLE or Sjögren syndrome. These antibodies are often present in the general population and particularly in patients with autoimmune thyroid disease or in first-degree relatives of patients with SLE. In addition, high titers of antinuclear antibodies do not necessarily indicate the presence of autoimmune disease.
Key Point
- Fibromyalgia is characterized by diffuse pain on both sides of the body and above and below the waist as well as axial skeletal pain.
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