Rheumatoid arthritis, a chronic and progressive disease, affects approximately 1.3 million Americans, according to the Arthritis Foundation. Classified as an autoimmune disease, RA occurs when the cells of the immune system mistakenly attack the cells in the synovial lining, the layer of tissue in the joint that provides cushion. Although the main symptoms of RA include joint swelling and pain, because it is a systemic disease, RA affects other areas of the body, resulting in symptoms similar to other diseases.
Joint Swelling and Pain
Other diseases that trigger an inflammatory response in the body can cause joint swelling and pain. Systemic lupus erythematosus, also classified as an autoimmune disease, affects approximately 1.5 million people in the United States, according to the Lupus Foundation. The most common symptom of SLE, joint pain, affects 90 percent of patients, as described by the University of Maryland Medical Center. Other diseases that can cause joint pain and swelling include ulcerative colitis and rheumatic fever.
Muscle Aches
The inflammation in the joints disrupts the ability to function normally, which can lead to muscle aches. A condition, known as fibromyalgia, causes widespread muscle pain, due to unknown causes. Patients often describe the pain of fibromyalgia as a deep, throbbing and twitching muscle ache, according to the National Fibromyalgia Association. Lyme disease, an infection caused by a bacterium transmitted through the bite of an infected tick, causes muscle aches and joint pain that can develop into arthritis-like symptoms.
Sjogren's Syndrome
RA affects the glands around the mouth and eyes, resulting in Sjogren's syndrome--a condition characterized by dry mouth and dry eyes. Additional symptoms associated with Sjogren's syndrome include swollen salivary glands, skin rashes, vaginal dryness, persistent dry cough and prolonged fatigue. Sjogren's syndrome occurs in conjunction with other autoimmune diseases, such as systemic lupus erythematosus.
Flu-Like Symptoms
During a flare-up, RA may cause flu-like symptoms, including a fever, muscle aches and weight loss. Many other conditions and diseases also cause flu-like symptoms. Meningitis, inflammation of the membrane, surrounding the brain and spinal cord, occurs as a result of a bacterial or viral infection. Although the initial symptoms resemble the flu, the disease can become serious and result in brain damage or death, according to MayoClinic.com. Other potentially serious diseases with flu-like symptoms include tuberculosis, an infection in the lungs, and hepatitis, inflammation of the liver.
Fatigue
Approximately 25 to 35 percent of patients with rheumatoid arthritis develop anemia, a low number of red blood cells, according to the The Johns Hopkins Arthritis Center. Because red blood cells carry oxygen to the cells throughout the body, anemia deprives cells of oxygen, resulting in fatigue. Hypothyroidism describes a condition in which the thyroid gland fails to produce enough thyroid hormones. Because these hormones regulate the conversion of food into energy, those with hypothyroidism have less energy therefore leading to fatigue. Systemic lupus erythematosus also causes fatigue.
