A 25-year-old woman presents to her primary care physician with joint and muscle pain. She has a general aching/pain in her joints that lasts all day. The pain is constant and is not relieved by rest or activity. She also has pain in her hands at times and occasionally notices trouble swallowing when she is eating. She has a medical history of anxiety and is not currently taking any medications. Her temperature is 98.6°F (37°C), blood pressure is 115/72 mmHg, pulse is 74/min, and respirations are 11/min. On physical exam, the patient is a healthy young woman with a sunburn. Her hands are mildly edematous with the findings in Figure A. Laboratory values are below:

Serum:
Na+: 145 mEq/L
K+: 4.4 mEq/L
Cl-: 100 mEq/L
HCO3-: 24 mEq/L
BUN: 9 mg/dL
Glucose: 70 mg/dL
Creatinine: .7 mg/dL
Ca2+: 10 mg/dL
Mg2+: 1.8 mEq/L

Which of the following antibodies is most likely to aid in making the diagnosis in this patient?
Anti-nuclear antibody
Anti-IgG Fc region
Anti-ribonuleoprotein
Anti-dsDNA
Anti-ribonuleoprotein
This patient is presenting with diffuse muscle/joint pain, Raynaud phenomenon, and dysphagia suggesting a diagnosis of mixed connective tissue disease. Anti-ribonucleoprotein (U1) antibodies are found in this disease.

Mixed connective tissue disease can present with a vast array of symptoms. The most common symptoms are Raynaud phenomenon (vascular hyper-reactivity that presents with burning/pain in the hands where the hands change color from white to blue to red, seen in Figure A), arthralgias, myalgias, dysphagia, and edema of the hands. Anti-U1 ribonucleoprotein antibodies are commonly found in mixed connective tissue disease and are a specific marker. In this disease, there is typically an absence of renal involvement. Treatment involves steroids as well as calcium channel blockers for symptomatic control of Raynaud phenomenon.

Batu et al. review the evidence regarding patients with mixed connective tissue disease. They found that many patients have overlapping symptoms with systemic lupus erythematosus and systemic sclerosis. They recommend studying patients with these mixed characteristics in order to better understand which treatment modalities are effective.

Figure/Illustration A is a clinical photograph showing the blanching of the distal fingers (red box). This finding demonstrates the Raynaud phenomenon during the early phase where the vessels have spasmed.

Incorrect Answers:
Answer A: Anti-dsDNA is a specific marker in systemic lupus erythematosus (SLE). SLE presents with SOAP BRAIN MD - Serositis, Oral ulcers, Arthritis, Photosensitivity, Blood disorders (hemolytic anemia, etc.), Renal involvement, ANA, Immune phenomena (anti-dsDNA, Smith), Neurological symptoms, Malar rash, and Discoid rash. Four of these criteria must be met to suspect a diagnosis of SLE. Treatment is with hydroxychloroquine.

Answer B: Anti-IgG Fc region is representative of rheumatoid factor which is found in rheumatoid arthritis. Rheumatoid arthritis can present with fever, weight loss, and joint pain that worsens in the morning and improves with activity. It is common for the joints of the hands to become deformed due to the disease process. Treatment is with methotrexate.

Answer C: Anti-nuclear antibodies (ANA) are likely positive in this patient; however, they are not more likely to aid in making the diagnosis than anti-ribonucleoprotein antibodies are. ANA are non-specific and can be found in many rheumatological conditions such as MCTD, lupus, and rheumatoid arthritis.

Answer E: Anti-Ro antibodies are found in Sjogren syndrome which presents with dry eyes, dry mouth, dental caries, and dyspareunia. A salivary gland biopsy can be used to confirm the diagnosis. Treatment includes artificial tears, vitamin D supplementation, and pilocarpine or cevimeline.

Bullet Summary:
Mixed connective tissue disease is associated with anti-ribonuleoprotein antibodies and presents with Raynaud phenomenon, arthralgia/arthritis, swollen hands, sclerodactyly, and myositis.