Systemic autoimmune and connective tissue diseases

Most discomfort addressed in body care can be explained in terms of posture, use, and recovery. However, descriptions such as swollen and painful joints, morning stiffness, stiff fingers, and a heavy feeling in the body also appear in explanations of systemic diseases involving the immune system. This document is a guide introducing twelve such conditions together.

There are three shared points worth knowing.

• “Systemic” does not mean symptoms are always present throughout the body. It refers to the potential involvement of multiple organs. At some times, only the joints may stand out; at others, only the skin or eyes may be prominent.
• Classification criteria are tools clinicians use to group patients according to consistent standards. They are not designed as self-checklists for matching symptoms. Diagnosis is based on the medical interview, physical examination, and blood and imaging tests considered together.
• There is considerable overlap between these diseases. Joint symptoms alone are difficult to use to distinguish them, which is why multiple symptoms are assessed together.

When multiple joints swell symmetrically on both sides, fever and fatigue persist regardless of activity, or joint symptoms occur alongside changes in the skin, mouth, or eyes, the condition is often assessed in a rheumatology department. Below is a closer look at each disease.

Systemic lupus erythematosus (SLE) is a major systemic autoimmune disease in which autoantibodies and immune complexes contribute to inflammation in multiple organs. It is known to be more common in women of childbearing age. Well-known features include a butterfly-shaped rash across the cheeks and bridge of the nose, and skin that is sensitive to sunlight.

The joints are among the most frequently affected areas. Stiffness, swelling, and pain affecting joints in both hands, wrists, and knees are commonly described. Although these features resemble rheumatoid arthritis, the two are classified as separate diseases because their immunological characteristics and the organs they affect differ. Timing patterns often mentioned in inflammatory joint diseases, such as morning stiffness, are also considered.

Research into its causes examines the combined effects of genetic predisposition, hormones, environmental factors, and changes in immune regulation. The disease often alternates between periods of worsening symptoms and quieter periods, making consistent long-term medical follow-up important.

Childhood-onset systemic lupus erythematosus (cSLE) is the name used when the same lupus begins at a young age. It is not a separate disease; the term distinguishes it by the timing of onset. The age thresholds used to distinguish childhood, adolescent, and adult onset vary somewhat between studies and healthcare systems.

Joint pain, joint stiffness, and arthritis are also commonly described in childhood lupus. It is therefore considered alongside various childhood conditions, including juvenile idiopathic arthritis. Because children are still growing, families often work together with clinicians to discuss and adjust everyday management, including school life, exercise, and sun exposure.

Drug-induced lupus (DIL) is a condition in which lupus-like symptoms and changes in immune test results appear after taking certain medications. Joint pain, muscle pain, fever, and skin changes are central features, and systemic forms and predominantly skin-related forms are sometimes discussed separately.

The medications reported to be associated with it are continually updated as new cases and pharmacovigilance data emerge. Lists circulating online may differ depending on when they were compiled. If you are concerned about a medication you take, the most reliable approach is to discuss it with the prescribing clinician rather than stopping it on your own.

Mixed connective tissue disease (MCTD) is a disease name developed to describe a condition in which features of lupus, systemic sclerosis, and inflammatory myopathy occur together in one person. It was introduced in the early 1970s by Sharp and colleagues in the United States and is closely associated with an autoantibody called anti-U1 RNP.

“Mixed” does not mean simply adding different diseases together. It refers to a clinical and immunological pattern that spans the boundaries of several conditions. Frequently described features include Raynaud phenomenon, swelling of the fingers and hands, and changes in the joints and muscles. Not all features appear at once, and the most prominent features may change over time. Involvement of internal organs such as the lungs, heart, and blood vessels has also been reported, so regular follow-up is maintained.

Undifferentiated connective tissue disease (UCTD) refers to a condition in which symptoms and test findings suggest an autoimmune connective tissue disease but do not fulfill all the classification criteria for a specific disease. “Undifferentiated” does not mean that symptoms are mild; it means that the information currently available does not allow classification as one particular disease.

It differs from MCTD, despite the similar names. MCTD is a disease defined around anti-U1 RNP and a particular pattern of overlap, whereas UCTD refers to a condition within a broader boundary area. With long-term observation, some cases develop into a defined connective tissue disease, while others remain unchanged or improve. Regular review over time is therefore important.

Systemic sclerosis is a systemic disease involving immune abnormalities, changes in small blood vessels, and fibrosis (hardening) of connective tissue. The name scleroderma comes from the meaning “hard skin.”

The fingers are the most visibly affected area. As the skin swells or becomes tight and hard, it can affect the ability to straighten and bend the fingers. Raynaud phenomenon, in which the fingers turn white and then blue in the cold, often occurs alongside it, but not everyone with Raynaud phenomenon has systemic sclerosis. Stiff fingers can also result from dryness, swelling, arthritis, or tendon problems, so see finger stiffness as well. The tissues involved and the areas affected differ from those in rheumatoid arthritis or Dupuytren contracture, in which connective tissue in the palm hardens.

Sjögren disease is a systemic disease in which immune responses affect exocrine glands such as the tear and salivary glands, causing dry eyes and mouth. It is named after Swedish ophthalmologist Henrik Sjögren, who reported the disease in the 1930s. The name Sjögren syndrome was also widely used in the past.

Typical features include a gritty feeling in the eyes, as if sand were present, and a dry mouth that makes dry foods difficult to swallow. Joint pain, joint stiffness, muscle pain, and fatigue may occur together, and pain in small joints such as those of the fingers and wrists or finger joint swelling may also be described. Dry eyes and mouth are also common because of age, environment, sleep, medication, or contact lenses, so if dryness persists, have the cause assessed by an ophthalmologist or internal medicine clinician.

Behçet disease is a systemic inflammatory disease in which recurrent mouth ulcers may be accompanied by inflammation in various combinations involving the skin, eyes, blood vessels, nervous system, and joints. It was reported in 1937 by Turkish dermatologist Hulusi Behçet. It is also called “Silk Road disease” because it is relatively common along the ancient Silk Road regions spanning Turkey, the Middle East, Korea, and Japan.

Symptoms do not all appear at the same time. A common pattern is for mouth ulcers alone to occur during one period, and eye or skin symptoms alone to appear and disappear during another. Joint symptoms are often described as temporary swelling and pain that then settle, affecting large and peripheral joints such as the knees, ankles, and wrists. Mouth sores that heal are common in anyone, so it is worth paying attention when they recur alongside other symptoms.

Adult-onset Still disease (AOSD) is a rare disease that begins in adulthood and involves systemic inflammatory symptoms such as high fever, a transient rash, joint pain or arthritis, and sore throat. “Still” in the disease name comes from British physician George Still, who reported inflammatory joint disease in children in the late 19th century.

A fever that rises and falls once or twice a day and a rash that appears and disappears with the fever are well-known features, but the combination and course vary from person to person. It shares many features with the systemic form of juvenile idiopathic arthritis, and research into the relationship between the two continues. It is also discussed from an autoinflammatory perspective, which differs from an autoimmune one. Fever and joint pain can also occur for common reasons such as infection, so if fever persists, bringing a record of temperature patterns to a medical appointment can be helpful.

Relapsing polychondritis is a rare systemic inflammatory disease involving repeated inflammation in cartilage-rich tissues such as the ears, nose, and airways. “Poly” in the name means that multiple sites can be involved, not that all cartilage is affected at once.

The best-known feature is redness, swelling, and pain in the outer ear. The earlobe, which contains no cartilage, is generally spared. The nasal cartilage, airways, joints, eyes, and inner ear may also be involved. Other conditions with similar features, such as VEXAS syndrome, have become recognized in recent years, so specialist assessment carefully distinguishes between them even when they look alike. Swelling and pain around the ear can also have common causes such as skin or soft-tissue infections, which should be considered as well.

Felty syndrome is a rare syndrome in which rheumatoid arthritis, neutropenia, and an enlarged spleen occur together. It was introduced in the 1920s by American physician Felty. Neutrophils are white blood cells involved in the early immune response against infection, and the spleen is an organ involved in blood and immune function.

It is known to occur in a very small proportion of people with rheumatoid arthritis. Low neutrophil counts can sometimes require greater attention to infection, so if you have had rheumatoid arthritis for a long time, reviewing blood test results with your clinician is important. Neutropenia and an enlarged spleen can also occur in other blood disorders or infections, so clinicians examine multiple possibilities from different angles.

Kawasaki disease is an acute systemic vasculitis that mainly affects children under 5 years of age. It was first reported in 1967 by Japanese pediatrician Tomisaku Kawasaki. Fever lasts for several days, accompanied by bloodshot eyes, redness of the lips and inside the mouth, swollen lymph nodes in the neck, and a body rash. Swelling and redness of the hands and feet may also occur.

Swollen and painful joints are sometimes reported as well, particularly in the knees, ankles, and hips. These symptoms generally do not persist for long, but in some cases they are observed for longer and considered alongside other forms of childhood arthritis. It is also worth remembering that regular follow-up examinations to assess the heart's blood vessels (the coronary arteries) continue after treatment.