Mixed connective tissue disease (MCTD) is a rare autoimmune disorder that affects various tissues and organs in the body, including the connective tissues, muscles, joints, skin, lungs, heart, and kidneys. MCTD is characterized by a combination of symptoms and laboratory findings associated with other connective tissue diseases such as systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and polymyositis.

The exact cause of MCTD is unknown, but it is believed to be related to a combination of genetic and environmental factors. The condition is most common in women in their 20s and 30s, but it can affect people of any age or gender.

Symptoms of MCTD can vary widely depending on which tissues and organs are affected, but they may include joint pain, swelling, and stiffness; muscle weakness; skin rashes and discoloration; Raynaud's phenomenon (discoloration of the fingers or toes in response to cold or stress); shortness of breath and other lung problems; heart problems such as pericarditis or arrhythmias; and kidney problems such as proteinuria.

Diagnosis of MCTD typically involves a physical exam, blood tests, and imaging studies to evaluate the affected tissues and organs. Treatment for MCTD may depend on the severity and progression of symptoms and may involve a combination of medications such as corticosteroids, immunosuppressants, and antimalarials to manage symptoms and prevent complications.

While there is no cure for MCTD, many people with the condition are able to manage their symptoms and maintain good health with appropriate medical care and lifestyle modifications such as regular exercise, stress reduction, and avoiding triggers such as sunlight or cold temperatures. Regular monitoring and management of symptoms are important for maintaining long-term health and preventing complications.

Mixed connective tissue disease is an autoimmune disorder, although the cause isn't known. In autoimmune disorders, your immune system — responsible for fighting off disease — mistakenly attacks healthy cells.

In connective tissue diseases, your immune system attacks the fibers that provide the framework and support for your body. Some people with mixed connective tissue disease have a family history of the condition. But the role of genetics in the disease remains unclear.

There's no cure for mixed connective tissue disease. Medication can help manage the signs and symptoms.

The type of medication prescribed depends on the severity of your disease and your symptoms. Medications can include:

• Corticosteroids. Drugs, such as prednisone (Deltasone, Rayos), can help prevent your immune system from attacking healthy cells and suppress inflammation. Side effects of corticosteroids can include mood swings, weight gain, high blood sugar, increased blood pressure, weakened bones and cataracts.
• Antimalarial drugs. Hydroxychloroquine (Plaquenil) can treat mild mixed connective tissue disease and might prevent flare-ups.
• Calcium channel blockers. This category of medications, including nifedipine (Adalat CC, Procardia) and amlodipine (Norvasc), that help relax the muscles in the walls of your blood vessels might be used to treat Raynaud's phenomenon.
• Other immunosuppressants. Your doctor might prescribe other medications based on your signs and symptoms. For example, if they're similar to those of lupus, your doctor might recommend medications typically prescribed for people with lupus.
• Pulmonary hypertension medications. Bosentan (Tracleer) or sildenafil (Revatio, Viagra) might be prescribed.