Systemic JIA is characterized by arthritis, fever, which typically is higher than the low-grade fever associated with polyarticular and a salmon pink rash. It accounts for 10-20% of JIA and affects males and females equally, unlike the other two subtypes of JIA, and affects adolescents. It generally involves both large and small joints. Systemic JIA can be challenging to diagnose because the fever and rash come and go. Fever can occur at the same time every day or twice a day (often in late afternoon or evening) with a spontaneous rapid return to baseline (vs. septic arthritis of continuous fever). The rash often occurs with fever. It is a discrete, salmon-pink macules of different sizes. It migrates to different locations on skin, rarely persisting in one location more than one hour. The rash is commonly seen on trunk and proximal extremities or over pressure areas.

Arthritis is often absent in the first weeks or even 6–8 months into the illness.

Systemic JIA may have internal organ involvement such as hepatosplenomegaly, lymphadenopathy, serositis, hepatitis, or tenosynovitis.

A polymorphism in macrophage migration inhibitory factor has been associated with this condition.

Three types of juvenile arthritis exist—juvenile rheumatoid arthritis (JRA), juvenile chronic arthritis (JCA), and juvenile idiopathic arthritis (JIA), of which JRA is the most common.

JRA again can be divided into three main forms: The classification is based upon symptoms, number of joints involved and the presence of certain antibodies in the blood.

1. Polyarticular arthritis is the first type of arthritis, which affects about 30–40% of children with arthritis and is more common in girls than boys. Typically five or more joints are affected (usually smaller joints such as the hands and feet but many also affect the hips, neck, shoulders and jaw).

2. Oligoarticular (aka pauciarticular) arthritis can be early or late onset and is the second type of arthritis, affecting about 50% of children with juvenile arthritis. This type affects fewer than four joints (usually the large joints such as knees, ankles or wrists) and may cause eye inflammation in girls with positive anti-nuclear antibodies (ANA). Girls younger than eight are more likely to develop this type of arthritis.

3. Systemic disease is the least common form, with 10–20% of children (boys and girls equally) being affected with limited movement, swelling and pain in at least one joint. A common symptom of this type is a high, spiking fever of or higher, lasting for weeks or months, and a rash of pale red spots on the chest, thighs or other parts of the body may be visible.

Systemic-onset juvenile idiopathic arthritis (also known as systemic juvenile idiopathic arthritis (sJIA) or the juvenile onset form of Still's disease) is a type of juvenile idiopathic arthritis (JIA) with extra-articular manifestations like fever and rash apart from arthritis. It was originally called systemic-onset juvenile rheumatoid arthritis or Still's disease.

Predominantly extra-articular manifestations like high fevers, rheumatic rash, enlargement of the liver and spleen, enlargement of the lymph nodes, and anemia. Others manifestations include inflammation of the pleura, inflammation of the pericardium, inflammation of the heart's muscular tissue, and inflammation of the peritoneum are also seen.

It is sometimes called "juvenile-onset Still's disease", to distinguish it from adult-onset Still's disease. However, there is some evidence that the two conditions are closely related.

Juvenile arthritis, also known as Childhood arthritis (JA) is any form of chronic arthritis or arthritis-related conditions which affects individuals under the age of 16.

Juvenile arthritis is a chronic autoimmune disease.

Symptoms of JIA are often nonspecific initially, and include lethargy, reduced physical activity, and poor appetite. The first manifestation, particularly in young children, may be limping. Children may also become quite ill, presenting with flu-like symptoms that persist. The cardinal clinical feature is persistent swelling of the affected joint(s), which commonly include the knee, ankle, wrist, and small joints of the hands and feet. Swelling may be difficult to detect clinically, especially for joints such as those of the spine, sacroiliac joints, shoulder, hip, and jaw, where imaging techniques such as ultrasound or MRI are very useful.

Pain is an important symptom. Morning stiffness that improves later in the day is a common feature (this implies inflammatory-type joint pain versus mechanical-type joint pain). Late effects of arthritis include joint contracture (stiff, bent joint due to fibrosis) and joint damage. Children with JIA vary in the degree to which they are affected by particular symptoms. Symptoms may also differ between sexes, affecting girls and boys differently among different geographic locations. This is predicted to be due to biological differences in different geographic regions. Children may also have swollen joints (inflammatory swelling, or in chronic arthritis due to synovial proliferation and thickening, and periarticular soft-tissue swelling).

The three major types of JIA are oligoarticular, polyarticular, and systemic.

Signs and symptoms of drug-induced lupus erythematosus include the following:

- Joint pain (arthralgia) and muscle pain (myalgia)

- Fatigue

- Serositis —inflammation of the tissues lining the heart and lungs.

- Anti-histone antibodies in 95% of cases

These signs and symptoms are not side effects of the drugs taken which occur during short term use. DIL occurs over long-term and chronic use of the medications listed below. While these symptoms are similar to those of systemic lupus erythematosus, they are generally not as severe unless they are ignored which leads to more harsh symptoms, and in some reported cases, death.

As many as 70% of people with lupus have some skin symptoms. The three main categories of lesions are chronic cutaneous (discoid) lupus, subacute cutaneous lupus, and acute cutaneous lupus. People with discoid lupus may exhibit thick, red scaly patches on the skin. Similarly, subacute cutaneous lupus manifests as red, scaly patches of skin but with distinct edges. Acute cutaneous lupus manifests as a rash. Some have the classic malar rash (or "butterfly rash") associated with the disease. This rash occurs in 30 to 60% of people with SLE.

Hair loss, mouth and nasal ulcers, and lesions on the skin are other possible manifestations.

SLE is one of several diseases known as "the great imitator" because it often mimics or is mistaken for other illnesses. SLE is a classical item in differential diagnosis, because SLE symptoms vary widely and come and go unpredictably. Diagnosis can thus be elusive, with some people having unexplained symptoms of SLE for years.

Common initial and chronic complaints include fever, malaise, joint pains, muscle pains, and fatigue. Because these symptoms are so often seen in association with other diseases, these signs and symptoms are not part of the diagnostic criteria for SLE. When occurring in conjunction with other signs and symptoms (see below), however, they are considered suggestive.

While SLE can occur in both males and females, it is found far more often in women, and the symptoms associated with each sex are different. Females tend to have a greater number of relapses, a low white blood cell count, more arthritis, Raynaud's phenomenon, and psychiatric symptoms. Males tend to have more seizures, kidney disease, serositis (inflammation of tissues lining the lungs and heart), skin problems, and peripheral neuropathy.

Palindromic rheumatism is a rare type of inflammatory arthritis which causes sudden inflammation in one or several joints, lasts a few hours or up to a few days, and then goes away completely. The problem usually involves 2 or 3 joints, which have onset over hours and last days to weeks, before subsiding. However episodes of recurrence form a pattern, with symptom-free periods between attacks lasting for weeks to months. The large joints are most commonly involved. Constitutionally, there may or may not be a fever, and swelling of the joints. The soft tissues are involved with swelling of the periarticular tissues, especially heel pads and finger pads. Nodules may be found in the subcutaneous tissues.Attacks may become more frequent with time but there is no joint damage after attacks.

It typically affects people between the ages of 20 and 50. One study showed an average age of onset of 49.

Clinical features may include constitutional symptoms like fever, loss of appetite, weight loss, fatigue, and kidney failure. A majority of patients may have blood in the urine and protein in the urine. Rapidly progressive glomerulonephritis may occur. Because many different organ systems may be involved, a wide range of symptoms are possible in MPA.

Purpura and livedo racemosa may be present.

Palindromic rheumatism is a disease of unknown cause. It has been suggested that it is an abortive form of rheumatoid arthritis (RA), since anti-cyclic citrullinated peptide antibodies (anti-CCP) and antikeratin antibodies (AKA) are present in a high proportion of patients, as is the case in rheumatoid arthritis. Unlike RA and some other forms of arthritis, palindromic rheumatism affects men and women equally. Palindromic rheumatism is frequently the presentation for Whipple disease which is caused by the infectious agent "Tropheryma whipplei" (formerly "T. whippelii").

Anti-citrullinated protein antibody is frequently associated.

MCTD combines features of scleroderma, myositis, systemic lupus erythematosus, and rheumatoid arthritis (with some sources adding polymyositis, dermatomyositis, and inclusion body myositis) and is thus considered an overlap syndrome.

MCTD commonly causes:

- joint pain/swelling,

- malaise,

- Raynaud phenomenon,

- muscle inflammation, and

- sclerodactyly (thickening of the skin of the pads of the fingers)

Drug-induced lupus erythematosus (DIL or DILE) is an autoimmune disorder (similar to systemic lupus erythematosus [SLE]) caused by chronic use of certain drugs. These drugs cause an autoimmune response (the body attacks its own cells) producing symptoms similar to those of SLE. There are 38 known medications to cause DIL but there are three that report the highest number of cases: hydralazine, procainamide, and isoniazid. While the criteria for diagnosing DIL has not been thoroughly established, symptoms of DIL typically present as muscle pain and joint pain. Generally, the symptoms recede after discontinuing use of the drugs.

Microscopic polyangiitis is an ill-defined autoimmune disease characterized by a systemic, pauci-immune, necrotizing, small-vessel vasculitis without clinical or pathological evidence of necrotizing granulomatous inflammation.

An overlap syndrome is an autoimmune disease of connective tissue in which a person presents with symptoms of two or more diseases.

Examples of overlap syndromes include mixed connective tissue disease and scleromyositis. Diagnosis depends on which diseases the patient shows symptoms and has positive antibodies for in their lab serology.

In overlap syndrome, features of the following diseases are found (most common listed):

- Systemic lupus erythematosus (SLE),

- Systemic sclerosis,

- Polymyositis,

- Dermatomyositis,

- Rheumatoid arthritis (RA)

- Sjögren's syndrome

- Eosinophilic granulomatosis with polyangiitis (EGPA)

- Autoimmune thyroiditis

- Antiphospholipid antibody syndrome

The treatment of overlap syndrome is mainly based on the use of corticosteroids and immunosuppressants. Biologic drugs, i.e. anti-TNFα or anti-CD20 monoclonal antibodies, have been recently introduced as alternative treatments in refractory cases. There are some concerns with the use of anti-TNF agents in patients with systemic autoimmune diseases due to the risk of triggering disease exacerbations.

Distinguishing laboratory characteristics are a positive, speckled anti-nuclear antibody and an anti-U1-RNP antibody.

The disease typically presents with joint pain, high fevers, a salmon-pink rash, enlargement of the liver and spleen, swollen lymph nodes, and an increased white blood cell count in the blood. Tests for rheumatoid factor and anti-nuclear antibodies are usually negative and serum ferritin is elevated. Patients experiencing a flare-up from Adult-onset Still's disease usually report extreme fatigue, swelling of the lymph nodes and, less commonly, fluid accumulation in the lungs and heart. In rare cases, AOSD can cause aseptic meningitis and sensorineural hearing loss.

The signs and symptoms of Kikuchi disease are fever, enlargement of the lymph nodes (lymphadenopathy), skin rashes, and headache. Rarely, enlargement of the liver and spleen and nervous system involvement resembling meningitis are seen. Often a bout of extreme fatigue can occur - often taking hold during latter parts of the day and the affected person can be more prone to fatigue from exercise.

A rare autoimmune disease characterized by recurrent urticaria (nettle rash), first described in the 1970s. There is no defined paradigm for the syndrome aetiology and severity in progression. Diagnosis is confirmed with the identification of at least two conditions from: venulitis on skin biopsy, arthritis, ocular inflammation, abdominal pain or positive C1q antibodies to immune complexes. It is this last category, anti-C1q antibodies, that all HUV patients test positive for. "In vitro" experiments and mouse models of the disease have not thoroughly determined the link between these antibodies and the disease, even though the link is so pronounced.

Urticarial vasculitis (also known as "chronic urticaria as a manifestation of venulitis", "hypocomplementemic urticarial vasculitis syndrome", "hypocomplementemic vasculitis" and "unusual lupus-like syndrome") is a skin condition characterized by fixed urticarial lesions that appear histologically as a vasculitis.

Possible symptoms include:

- General symptoms: Fever, weight loss

- Skin: Palpable purpura, livedo reticularis

- Muscles and joints: Myalgia or myositis, arthralgia or arthritis

- Nervous system: Mononeuritis multiplex, headache, stroke, tinnitus, reduced visual acuity, acute visual loss

- Heart and arteries: Myocardial infarction, hypertension, gangrene

- Respiratory tract: Nose bleeds, bloody cough, lung infiltrates

- GI tract: Abdominal pain, bloody stool, perforations

- Kidneys: Glomerulonephritis

In the skin, systemic sclerosis causes hardening and scarring. The skin may appear tight, reddish, or scaly. Blood vessels may also be more visible. Where large areas are affected, fat and muscle wastage may weaken limbs and affect appearance. Patients report severe and recurrent itching of large skin areas. The severity of these symptoms varies greatly among patients: Some having scleroderma of only a limited area of the skin (such as the fingers) and little involvement of the underlying tissue, while others have progressive skin involvement. Digital ulcers — open wounds on especially on fingertips and less commonly the knuckles — are not uncommon.

People with AOSD generally experience one of two patterns in the disease:

- a debilitating pattern of fevers, pain, and other systemic symptoms, or

- a somewhat less aggressive pattern, in which the main symptom is arthritis and chronic joint pain.

One set of 21 adult-onset Still's disease patients were divided into four types, according to clinical course patterns. These included monocyclic systemic disease, polycyclic systemic disease, chronic articular monocyclic systemic disease, and chronic articular polycyclic systemic disease. People with chronic articular disease and polyarticular disease were at higher risk to develop disabling arthritis.

Vasculitis can be classified by the cause, the location, the type of vessel or the size of vessel.

- "Underlying cause". For example, the cause of syphilitic aortitis is infectious (aortitis simply refers to inflammation of the aorta, which is an artery.) However, the causes of many forms of vasculitis are poorly understood. There is usually an immune component, but the trigger is often not identified. In these cases, the antibody found is sometimes used in classification, as in ANCA-associated vasculitides.

- "Location of the affected vessels". For example, ICD-10 classifies "vasculitis limited to skin" with skin conditions (under "L"), and "necrotizing vasculopathies" (corresponding to systemic vasculitis) with musculoskeletal system and connective tissue conditions (under "M"). Arteritis/phlebitis on their own are classified with circulatory conditions (under "I").

- "Type or size of the blood vessels" that they predominantly affect. Apart from the arteritis/phlebitis distinction mentioned above, vasculitis is often classified by the caliber of the vessel affected. However, there can be some variation in the size of the vessels affected.

According to the size of the vessel affected, vasculitis can be classified into:

- Large vessel: Polymyalgia rheumatica, Takayasu's arteritis, Temporal arteritis

- Medium vessel: Buerger's disease, Kawasaki disease, Polyarteritis nodosa

- Small vessel: Behçet's syndrome, Eosinophilic granulomatosis with polyangiitis, Cutaneous vasculitis, Henoch–Schönlein purpura, Microscopic polyannulomatosis ConditionofSome disorders have vasculitis as their main feature. The major types are given in the table below:

Takayasu's arteritis, polyarteritis nodosa and giant cell arteritis mainly involve arteries and are thus sometimes classed specifically under arteritis.

Furthermore, there are many conditions that have vasculitis as an accompanying or atypical feature, including:

- Rheumatic diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and dermatomyositis

- Cancer, such as lymphomas

- Infections, such as hepatitis C

- Exposure to chemicals and drugs, such as amphetamines, cocaine, and anthrax vaccines which contain the Anthrax Protective Antigen as the primary ingredient.

In pediatric patients varicella inflammation may be followed by vasculitis of intracranial vessels. This condition is called post varicella angiopathy and this may be responsible for arterial ischaemic strokes in children.

Several of these vasculitides are associated with antineutrophil cytoplasmic antibodies. These are:

- Granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis)

- Eosinophilic granulomatosis with polyangiitis (formerly known as Churg-Strauss syndrome)

- Microscopic polyangiitis