A 28 year old woman comes to clinic for evaluation of diffuse pain. The patient complains of widespread myalgias and arthralgias for the past three months. The pain is aching in quality and is becoming severe. It interferes with her activities such as cleaning the house and shopping. She also complains of fatigue but has no difficulty with sleep or morning stiffness. A review of systems is negative for weight loss, fever, rash, paresthesias, weakness, joint swelling, and Raynaud's phenomenon. The patient does complain of dry skin and mild constipation.

The patient has no significant prior medical history and takes no medications, but she takes many over the counter vitamins and supplements.

The general medical examination is unremarkable. There is some tenderness on palpation of the joints and muscles but no joint swelling, warmth, or effusion. There is no rash and the neurologic examination is intact except for a delay in the relaxation phase of the deep tendon reflexes.

What is the differential diagnosis?

The differential diagnosis of diffuse arthralgias and myalgias includes the onset of an inflammatory rheumatic disease such as systemic lupus erythematosus or rheumatoid arthritis, a soft tissue syndrome such as fibromyalgia, somatization disorder or depression, endocrinopathy, infection such as a viral arthritis or Lyme disease, and toxic or drug reaction.

What tests may be helpful in making a diagnosis?

Despite the broad differential diagnosis, there are several clues to a specific diagnosis in the history and physical examination of this patient. Dry skin, constipation, fatigue, myalgias, and arthralgias are possible manifestations of hypothyroidism. Delayed relaxation phase of the deep tendon reflexes is also consistent with a diagnosis of hypothyroidism. Thyroid function tests should be requested. Other useful tests may include ESR, CBC, Chemistry, CPK, anti-nuclear antibody (ANA), and Rheumatoid Factor (RF).