Autoimmune Rheumatic Diseases: Diagnosis and Management
Autoimmune rheumatic diseases (ARDs) are a diverse group of conditions that primarily affect the joints, bones, muscle, and connective tissue (see Sidebar).1 They can be especially challenging to diagnose during early stages, often presenting with nonspecific symptoms and signs that may flare and remit. However, early diagnosis is important to improve outcomes for patients.
This article will review ARDs and the importance of early and accurate diagnosis. It will discuss the importance of laboratory testing for autoantibodies and how antibody panels can help to rule in or rule out common autoimmune diseases. Also discussed is the importance of laboratory testing before and after biologic drugs are administered for treatment of ARDs.
Characteristics of ARDs
The ARDs are characterized by an abnormal immune response to normal cells and tissues.1,2 They can lead to severe, debilitating pain and progressive disease. Some are associated with increased morbidity and mortality. The abnormal immune response can be directed at a specific part of the body, such as the joints in rheumatoid arthritis (RA).2 However, it can also be more general and systemic, affecting multiple organs and tissues as with systemic lupus erythematosus (SLE).2 The majority of rheumatic diseases are due to an autoimmune response,1 whereas others (eg, gout and osteoarthritis) have different pathophysiology.
Scope and Causes
The overall prevalence of autoimmunity in the general population is approximately 3% to 5%.2 Women get autoimmune diseases at a rate more than twice that of men (6.4% of women compared to 2.7% of men).3 Different autoimmune diseases can occur at different times in a person’s life. However, women are most commonly diagnosed with an autoimmune disease when they are between 14 and 44 years old.3
Some ARDs, such as SLE, have a genetic component, and can also be triggered by infections or environmental factors.2 However, the cause of an ARD in a specific individual usually cannot be determined.
Diagnosis of ARDs
Diagnosis of ARDs may be delayed because initial signs and symptoms can be nonspecific. If diagnosis is delayed, irreversible joint or organ damage may ensue. Early diagnosis and treatment provides an opportunity to prevent or mitigate this damage, control symptoms, and improve chances for remission.2,4
Signs and Symptoms
Some ARDs have characteristic findings that can aid in diagnosis. For example, the primary symptoms of Sjögren syndrome are dry mouth and dry eyes.5 Other ARDs have characteristic radiographic findings.6-8
However, pathognomonic signs are the exception rather than the rule. The early symptoms of autoimmune diseases may flair and remit and may overlap with those of other conditions, including other ARDs. They may include2,4
- Muscle aches
- Swelling and redness over the joints
- Mild fever
- Trouble concentrating
- Hair loss
- Numbness and tingling in the hands and feet
Autoantibody testing is an important aid in the diagnosis of ARDs.2,9 Almost all ARDs have specific autoantibody profiles (eg, myositis- and systemic sclerosis-specific antibodies). As such, testing for specific autoantibodies can help rule in or rule out specific ARDs. Testing using antibody panels (testing for a number of autoantibodies at the same time) can improve efficiency over sequential testing, expedite diagnosis and treatment, and improve outcomes for patients. Testing patients with risk factors for certain ARDs is also valuable. For example, SLE autoantibodies can be detected many years before a patient becomes symptomatic.10
No single therapy exists for ARDs. Treatments include nonsteroidal anti-inflammatory drugs, immunosuppressants, and cytokine antagonists.2 In general, autoimmune conditions are not cured; treatments are aimed at minimizing symptoms, inhibiting inflammation, slowing progression, and/or inducing remission.2
Biologics and Biosimilars
Many ARDs are treated with biologics or biosimilars. A biologic is a drug that contains components of a living organism or is manufactured in a living system, such as microorganisms, plant cells, or animal cells.11 Many biologics are produced using recombinant DNA technology; others are monoclonal antibodies, including adalimumab, ustekinumab, and infliximab.12-14 A biosimilar is a biologic medical product that is an almost identical copy of an original product.11 Examples include Inflectra™ and Renflexis™, which are biosimilars of Remicade® (infliximab).
Biologics and biosimilars alter the function of the immune system, and alterations of immune function can result in certain latent infections becoming active.14 Thus, laboratory testing for certain infections is essential prior to treatment. Medical professional organization guidelines recommend testing for hepatitis B virus (HBV), hepatitis C virus (HCV), and/or tuberculosis prior to beginning treatment with a biologic or biosimilar.12,15