A 27-year-old woman presents to her primary care physician with pain in her hands, shoulders, and knees. The pain has lasted for several months but seems to have worsened recently. Any activity such as opening jars, walking, or brushing her teeth is painful. The patient has a medical history of a suicide attempt in college, constipation, anxiety, depression, and a sunburn associated with surfing which was treated with aloe vera gel. Her temperature is 99.5°F (37.5°C), blood pressure is 137/78 mmHg, pulse is 92/min, respirations are 14/min, and oxygen saturation is 98% on room air. Laboratory values are obtained and shown below. Hemoglobin: 9 g/dL Hematocrit: 33% Leukocyte count: 2,500/mm^3 with normal differential Platelet count: 107,000/mm^3 Serum: Na+: 139 mEq/L Cl-: 102 mEq/L K+: 4.4 mEq/L HCO3-: 24 mEq/L BUN: 21 mg/dL Glucose: 90 mg/dL Creatinine: 1.0 mg/dL Ca2+: 10.2 mg/dL AST: 12 U/L ALT: 10 U/L Which of the following findings is the most likely to be positive in this patient?
Anti-cyclic citrullinated peptide antibodies
Degenerated cartilage in weight bearing joints
Anti-dsDNA antibodies
Anti-histone antibodies
Anti-dsDNA antibodies
This patient is presenting with arthralgias, pancytopenia, possible malar rash, and a history of depression/abnormal behavior. Epidemiologically, the most likely diagnosis is systemic lupus erythematosus (SLE) which is associated with anti-dsDNA antibodies.

SLE is an autoimmune disorder that most commonly occurs in young adult women. It presents with at least 4 criteria from SOAP BRAIN MD - Serositis, Oropharyngeal ulcers, Anti-nuclear antibodies, Photosensitivity, Blood disorders (pancytopenia and hemolytic anemia), Renal abnormalities (proteinuria), Arthralgias, Immune disease (hemolytic anemia and anti-dsDNA), Neurologic (psychosis, stroke, and seizure), Malar rash, and Discoid rash. The most common presenting symptoms for SLE can often be just arthralgias/arthritis with vague other symptoms suggestive of a rheumatologic disorder. Anti-nuclear antibodies are very sensitive for this pathology and anti-dsDNA antibodies are very specific. Treatment may include hydroxychloroquine as well as other immunomodulators and management of end-organ dysfunction.

Wang and Xia review the evidence regarding double stranded DNA in patients with SLE. They discuss how these antibodies are a very specific finding in this disease. They recommend measuring these levels.

Incorrect Answers:
Answer A: Anti-cyclic citrullinated peptide is associated with rheumatoid arthritis which is a possible diagnosis in this patient, but it is less likely epidemiologically given her age and other symptoms of pancytopenia and a history of sunburn (which is likely a malar rash or photosensitivity). Treatment is with methotrexate.

Answer C: Anti-histone antibodies would be found in drug-induced lupus. This patient's medication history is not known; however, this is a less likely diagnosis compared to SLE. Treatment is with discontinuation of the offending medication.

Answer D: Degenerated cartilage in weight bearing joints describes osteoarthritis which tends to affect the knees and hips in older patients. Treatment is with conservative management or with total joint replacement.

Answer E: IgM against parvovirus B19 describes a parvovirus B19 infection which commonly presents with arthralgias; however, her other symptoms point towards a diagnosis of SLE. Treatment is supportive.

Bullet Summary:
Arthritis/arthralgias are often the most common presenting symptom for SLE.