IgG4-related disease has been described as an indolent condition. Although possibly based on opinion rather than on objective assessments, symptoms, if any, are commonly described as mild in the medical literature. This can be in spite of considerable underlying organ destruction. People are often described as being generally well at the time of diagnosis, although some may give a history of weight loss.

Pain is generally not a feature of the inflammation. However it may occur as a secondary effect, for example due to either obstruction or compression.

Often diagnosis is made due to the presence of painless swellings or mass lesions, or due to complications of masses, e.g. jaundice due to involvement of the pancreas, biliary tree or liver. Symptoms are commonly attributed to other conditions and other diagnoses may have been made years before diagnosis, e.g. urinary symptoms in men attributed to common prostate conditions. Lesions may also be detected incidentally on radiological images, but can be easily misdiagnosed as malignancies.

Reported cases do include some significant symptoms or findings however:

Several case studies on IgG4-related prostatitis have been reported. Patients have been noted to commonly present with lower urinary tract symptoms such as dysuria, pollakisuria, urinary urgency, and a feeling of incomplete emptying. The clinical presentation is similar to that in benign prostatic hyperplasia or chronic prostatitis, although pain, as occurs in CP/CPPS, does not usually appear to be significant.

Men with IgG4-related prostatitis may have similar findings to those that are frequently, but not always, seen in other organ manifestations of IgG4-related disease, such as elevated blood levels of IgG4, IgE and eosinophils.

FDG-PET scans have been reported to be useful as a diagnostic modality for detecting IgG4-related prostatitis in men with IgG4-RD.

IgG4-related disease (IgG4-RD), formerly known as IgG4-related systemic disease, is a chronic inflammatory condition characterized by tissue infiltration with lymphocytes and IgG4-secreting plasma cells, various degrees of fibrosis (scarring) and a usually prompt response to oral steroids. In approximately 51–70% of people with this disease, "serum" IgG4 concentrations are elevated during an acute phase.

It is a relapsing–remitting disease associated with a tendency to mass forming, tissue-destructive lesions in multiple sites, with a characteristic histopathological appearance in whichever site is involved. Inflammation and the deposition of connective tissue in affected anatomical sites can lead to organ dysfunction, or even organ failure, if not treated.

Early detection is important to avoid organ damage and potentially serious complications. Treatment is recommended in all symptomatic cases of IgG4-RD and also in asymptomatic IgG4-RD involving certain anatomical sites.

Patients mostly present with a hard lump in one breast without any sign of a systemic disease. Other possible symptoms include nipple retraction, pain, inflammation of the overlying skin, nipple discharge, fistula, enlarged lymph nodes, in rare case peau d'orange-like changes.

Presentation is mostly unilateral although a significant share of cases is bilateral, also in many cases contralateral or bilateral recurrences were documented.

Several cases occurring together with fever, polyarthralgia and erythema nodosum were documented.

Characteristic for idiopathic granulomatous mastitis are multinucleated giant cells and epithelioid histiocytes forming non-caseating granulomas around lobules. Often minor ductal and periductal inflammation is present. The lesion is in some cases very difficult to distinguish from breast cancer and other causes such as infections (tuberculosis, syphilis, corynebacterial infection, mycotic infection), autoimmune diseases (sarcoidosis, granulomatosis with polyangiitis), foreign body reaction and granulomatous reaction in a carcinoma must be excluded.

The condition is diagnosed very rarely. As the diagnosis is a lengthy differential diagnosis of exclusion there is considerable uncertainty about incidence. It has been suspected that some cases diagnosed as IGM in developing countries may have other explanations. On the other hand, IGM is usually diagnosed only after complications and referral to a secondary breast care center so light cases may resolve spontaneously or after symptomatic treatment and thus never be diagnosed as IGM. As a completely pathogen free breast will be exceedingly rare even in completely healthy population there is also uncertainty when to consider pathogens as causative or as mere coincidental finding.

Affected individuals typically present with sudden painful proptosis, redness, and edema. Proptosis will vary according to the degree of inflammation, fibrosis, and mass effect. Occasionally, ptosis, chemosis, motility dysfunction (ophthalmoplegia), and optic neuropathy are seen. In the setting of extensive sclerosis there may be restriction, compression, and destruction of orbital tissue. Symptoms usually develop acutely (hours to days), but have also been seen to develop over several weeks or even months.Malaise, headaches, and nausea may accompany these symptoms. Other unusual presentations described include cystoid macular edema, temporal arteritis, and cluster headaches.

Pediatric IOI accounts for about 17% of cases idiopathic orbital inflammation. The most common sign is proptosis, but redness and pain are also experienced. Presentation varies slightly compared to adults with bilateral involvement, uveitis, disc edema and tissue eosinophilia being more common in this population. The presence of uveitis generally implies a poor outcome for pediatric IOI. Bilateral presentation may have a higher incidence of systemic disease.

Idiopathic granulomatous mastitis is defined as granulomatous mastits without any other attributable cause such as those above mentioned. It occurs on average two years and almost exclusively up to six years after pregnancy, usual age range is 17 to 42 years. Some cases have been reported that were related to drug induced hyperprolactinemia.

Exceptionally rarely it has been diagnosed during pregnancy and in men.

"Chronic nonspecific parotitis:"

This term is generally used for patients in whom no definite cause is found. Episodes may last for several days, paralleling the time course of a bacterial or viral illness. Others may experience episodes that last only a few hours from onset to resolution. Some episodes may last for several weeks. Quiescent periods between episodes last for hours, days, or even years.

"Recurrent parotitis of childhood:"

An uncommon syndrome in which recurring episodes clinically resembling mumps. Generally, episodes begin by age 5 years, and virtually all patients become asymptomatic by age 10–15 years. The duration of attacks averages 3–7 days but may last 2–3 weeks in some individuals. The spectrum varies from mild and infrequent attacks to episodes so frequent that they prevent regular school attendance.

Local heat applied to the gland, massaging the gland from back to front, and taking penicillin usually cure individual episodes. Treatment of individual infections may prevent injury to the gland parenchyma. Severe disease may be treated by parotidectomy.

"Sialadenosis (sialosis):"

In this disorder, both parotid glands may be diffusely enlarged with only modest symptoms. Patients are aged 20–60 years at onset, and the sexes are equally involved. The glands are soft and non-tender. Approximately half of the patients have endocrine disorders such as diabetes, nutritional disorders such as pellagra or kwashiorkor, or have taken drugs such as guanethidine, thioridazine, or isoprenaline.

"Sarcoidosis:"

The lungs, skin, and lymph nodes are most often affected, but the salivary glands are involved in approximately 10% of cases. Bilateral firm, smooth, and non-tender parotid enlargement is classic. Xerostomia occasionally occurs. The Heerfordt-Waldenstrom syndrome consists of sarcoidosis with parotid enlargement, fever, anterior uveitis, and facial nerve palsy.

"IgG4-related sialadenitis":

This term refers to IgG4-related disease (IgG4-RD) involving any of the major salivary glands, i.e. parotid or submandibular glands. This is often symmetrical and is usually associated with manifestations of IgG4-RD elsewhere in the body. IgG4-related sialadenitis is particularly associated with involvement of one or both of the lacrimal glands (referred to as IgG4-related dacryo-sialadenitis). "Mikulicz's disease", now considered to be a subtype of IgG4-related disease, was a term used when (i) any two of the parotid, submandibular and lacrimal glands were persistently and symmetrically enlarged and (ii) other diseases that may mimic this presentation were excluded.

"Pneumoparotitis:"

Air within the ducts of the parotid gland with or without inflammation. The duct orifice normally functions as a valve to prevent air from entering the gland from a pressurized oral cavity. Rarely, an incompetent valve allows insufflation of air into the duct system. Pneumoparotitis most commonly occurs in wind instrument players, glass blowers, and scuba divers.

Several lymph nodes reside within the parotid gland as a superficial and deep group of nodes. These nodes may be involved with any process that affects lymph nodes, including bacterial, fungal, viral, and neoplastic processes. Rarely, drugs such as iodides, phenylbutazone, thiouracil, isoproterenol, heavy metals, sulfisoxazole, and phenothiazines cause parotid swelling.

These are also collectively known as chronic punctate parotitis or chronic autoimmune parotitis.

"Sjögren's syndrome:"

Chronic inflammation of the salivary glands may also be an autoimmune disease known as Sjögren's syndrome. The disease most commonly appears in people aged 40–60 years, but it may affect small children. In Sjögren syndrome, the prevalence of parotitis in women versus men is approximately 9:1. The involved parotid gland is enlarged and tender at times. The cause is unknown. The syndrome is often characterized by excessive dryness in the eyes, mouth, nose, vagina, and skin.

"Lymphoepithelial lesion of Godwin:"

Most frequently associated with a circumscribed tumor with the histologic features of Sjögren syndrome. This designation has also fallen out of favour.

Symptoms, if any, can be mild even in the presence of significant swelling or masses.

Lacrimal gland involvement may cause swelling of the upper eyelid, or proptosis if there is severe swelling. Other orbital masses or inflammation can result in visual disturbance (blurred vision, double vision, visual field impairment), restricted eye movements, pain or discomfort, numbness in the distribution of the supraorbital and/or infraorbital nerves, or proptosis.

IgG4-related ophthalmic disease has been estimated to account for approximately 25% of all cases of proptosis, eyelid swelling and other features of orbital swelling.

This inflammation has a number of possible causes, including trauma, viral or bacterial infections (notably, syphilis), and certain immune disorders and connective tissue diseases.

Aortitis is most commonly seen in patients with syphilis, autoimmune vasculitis (giant cell arteritis, Takayasu's arteritis), polymyalgia rheumatica, and rheumatoid arthritis. IgG4-related disease has more recently been identified as a cause of aortitis, and also as a cause of periaortitis (inflammation "surrounding" the aorta).

There is a wide range of symptoms that are dependent on the location of the aortic inflammation or associated disorder. A few symptoms recognized in patients are fever, chills, muscle pains, and malaise (general discomfort). In addition, hypertension (high blood pressure) may occur. Hypertension happens when the renal artery narrows and elasticity of the aorta and branches decrease.

Riedel's thyroiditis, also called Riedel's struma is a chronic form of thyroiditis.

It is now believed that Riedel's thyroiditis is one manifestation of a systemic disease that can affect many organ systems called IgG4-related disease. It is often a multi-organ disease affecting pancreas, liver, kidney, salivary and orbital tissues and retroperitoneum. The hallmarks of the disease are fibrosis and infiltration by IgG4 secreting plasma cells.

Giant-cell arteritis and Takayasu's arteritis have much in common, but usually affect patients of different ages, with Takayasu's arteritis affecting younger people, and giant-cell arteritis having a later age of onset.

Aortitis can also be considered a large-vessel disease.

Takayasu arteritis. Primarily affects the aorta and its main branches. At least 3 out of 6 criteria yields sensitivity and specificity of 90.5 and 97.8%:

- onset < 40 years affects young and middle -aged women (ages 15–45)

- claudication of extremities

- decreased pulsation of one or both brachial arteries

- at least 10 mmHg systolic difference in both arms

- bruit over one or both carotid arteries or abdominal aorta

- arteriographic narrowing of aorta, its primary branches, or large arteries in upper or lower extremities

- Ocular manifestation

- visual loss or field defects

- Retinal hemorrhages

- Neurological abnormalitis

- Treatment: steroids

Giant cell (temporal) arteritis. Chronic vasculitis of both large and medium vessels, primarily affecting cranial branches of the arteries arising from the aortic arch. At least 3 out of 5 criteria yields sensitivity and specificity of 95 and 91%:

- Age at onset ≥ 50 years

- New onset headache with localized tenderness

- Temporal artery tenderness or decreased pulsation

- Elevated ESR ≥ 50 mm/hour Westergren

- Temporal artery biopsy showing vasculitis with mononuclear cell infiltrate or granulomatous inflammation, usually with multinucleated giant cells

These conditions are sometimes considered together with the small vessel vasculitides.

Polyarteritis nodosa (PAN). Systemic necrotizing vasculitis and aneurysm formation affecting both medium and small arteries. If only small vessels are affected, it is called microscopic polyangiitis, although it is more associated with granulomatosis with polyangiitis than to classic PAN. At least 3 out of 10 criteria yields sensitivity and specificity of 82 and 87%:

- unexplained weight loss > 4 kg

- livedo reticularis

- testicular pain

- myalgias, weakness

- Abdominal pain, diarrhea, and GI bleeding

- mononeuropathy or polyneuropathy

- new onset diastolic blood pressure > 90 mmHg

- elevated serum BUN (> 40 mg/dL) or serum creatinine (> 1.5 mg/dL)

- hepatitis B infection

- arteriographic abnormalities

- arterial biopsy showing polymorphonuclear cells

Kawasaki disease. Usually in children(age<4), it affects large, medium, and small vessels, prominently the coronary arteries. Associated with a mucocutaneous lymph node syndrome. Diagnosis requires fever lasting five days or more with at least 4 out of 5 criteria:

- bilateral conjunctival injection

- injected or fissured lips, injected pharynx, or strawberry tongue

- erythema of palms/soles, edema of hands/feet, periungual desquamation

- polymorphous rash

- cervical lymphadenopathy (at least one node > 1.5 cm)

Isolated cerebral vasculitis. Affects medium and small arteries over a diffuse CNS area, without symptomatic extracranial vessel involvement. Patients have CNS symptoms as well as cerebral vasculitis by angiography and leptomeningeal biopsy.

Reactive arthritis, also known as Reiter's syndrome, is a form of inflammatory arthritis that develops in response to an infection in another part of the body (cross-reactivity). Coming into contact with bacteria and developing an infection can trigger the disease. By the time the patient presents with symptoms, often the "trigger" infection has been cured or is in remission in chronic cases, thus making determination of the initial cause difficult.

The arthritis often is coupled with other characteristic symptoms; this has been called Reiter's syndrome, Reiter's disease or Reiter's arthritis. The term "reactive arthritis" is increasingly used as a substitute for this designation because of Hans Conrad Julius Reiter's war crimes with the Nazi Party. The manifestations of reactive arthritis include the following triad of symptoms: an inflammatory arthritis of large joints, inflammation of the eyes in the form of conjunctivitis or uveitis, and urethritis in men or cervicitis in women. Arthritis occurring alone following sexual exposure or enteric infection is also known as reactive arthritis. Patients can also present with mucocutaneous lesions, as well as psoriasis-like skin lesions such as circinate balanitis, and keratoderma blennorrhagicum. Enthesitis can involve the Achilles tendon resulting in heel pain. Not all affected persons have all the manifestations.

The clinical pattern of reactive arthritis commonly consists of an inflammation of fewer than five joints which often includes the knee or sacroiliac joint. The arthritis may be "additive" (more joints become inflamed in addition to the primarily affected one) or "migratory" (new joints become inflamed after the initially inflamed site has already improved).

Reactive arthritis is an RF-seronegative, HLA-B27-linked arthritis often precipitated by genitourinary or gastrointestinal infections. The most common triggers are intestinal infections (with "Salmonella", "Shigella" or "Campylobacter") and sexually transmitted infections (with "Chlamydia trachomatis").

It most commonly strikes individuals aged 20–40 years of age, is more common in men than in women, and more common in white than in black people. This is owing to the high frequency of the HLA-B27 gene in the white population. It can occur in epidemic form. Patients with HIV have an increased risk of developing reactive arthritis as well.

A large number of cases during World Wars I and II focused attention on the triad of arthritis, urethritis, and conjunctivitis (often with additional mucocutaneous lesions), which at that time was also referred to as Fiessenger-Leroy-Reiter syndrome.

A differential diagnosis includes lymphoproliferative lesions, thyroid ophthalmopathy, IgG4-related ophthalmic disease, sarcoidosis, granulomatosis with polyangiitis, orbital cellulitis and carotid-cavernous fistula.

If untreated, has three distinct phases. The first is a prepulseless inflammatory stage with nonspecific symptoms such as fatigue, arthralgias, and low-grade fevers. Phase two includes vascular inflammation with pain secondary to the condition, along with tenderness to palpation over the site. The last phase includes symptoms of ischemia and pain associated with the use of limbs. Limbs are also cool and clammy in this stage.

The extent of inflammation that can occur in IgG4-ROD is well demonstrated on magnetic resonance imaging (MRI).

Infraorbital nerve enlargement (IONE) is considered to be a particularly suspicious sign of IgG4-ROD, but seems to occur only when inflammation is in direct contact with the infraorbital canal. IONE is defined as the infraorbital nerve diameter being greater than the optic nerve diameter in the coronal plane.

The inflammatory lesions in Küttner's tumor may occur on one side (unilateral) or both sides (bilateral), predominantly involving the submandibular gland, but is also known to occur in other major and minor salivary glands, including the parotid gland.

Overall, salivary gland tumors are relatively rare, with approximately 2.5–3 cases per 100,000 people per year seen in the Western world; however, salivary gland malignancies account for 3–5% of all head and neck cancers. However, salivary tumors show a great deal of morphological diversity, as well as variations in the nature of the lesion (malignant vs. benign): approximately 20% to 25% of parotid tumors, 35% to 40% of submandibular tumors, and more than 90% of sublingual gland tumors are malignant. This situation underscores the diagnostic challenges in respect of Küttner's tumor; despite being benign, this condition mimics the clinical appearance of malignancy in the salivary gland.

The swollen masses of Küttner's tumor are generally painful, and patients are advised surgical resection (known as 'sialadenectomy') of a part or whole of the glandular tissue upon suspicion of possible malignancy. It is only upon post-surgical histopathology of the excised mass that the diagnosis of Küttner's tumor is definitively made.

Chronic sclerosing sialadenitis is a chronic (long-lasting) inflammatory condition affecting the salivary gland. Relatively rare in occurrence, this condition is benign, but presents as hard, indurated and enlarged masses that are clinically indistinguishable from salivary gland neoplasms or tumors. It is now regarded as a manifestation of IgG4-related disease.

Involvement of the submandibular glands is also known as Küttner's tumor, named after Hermann Küttner (1870–1932), a German Oral and Maxillofacial Surgeon, who reported four cases of submandibular gland lesions for the first time in 1896.

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

Although a clear understanding of the various skin lesions in IgG4-related disease is a work in progress, skin lesions have been classified into subtypes based on documented cases:

- Angiolymphoid hyperplasia with eosinophilia (or lesions that mimic it) and cutaneous pseudolymphoma

- Cutaneous plasmacytosis

- Eyelid swelling (as part of Mikulicz's disease)

- Psoriasis-like eruptions

- Unspecified maculopapular or erythematous eruptions

- Hypergammaglobulinemic purpura and urticarial vasculitis

- Impaired blood supply to fingers or toes, leading to Raynaud's phenomenon or gangrene

Note:

In addition, Wells syndrome has also been reported in a case of IgG4-related disease.

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

IgG4-related skin disease is the recommended name for skin manifestations in IgG4-related disease (IgG4-RD). Multiple different skin manifestations have been described.

Some specific reactive lymphadenopathies with a predominantly follicular pattern:

- Rheumatoid arthritis

- Sjogren syndrome

- IgG4-related disease (IgG4-related lymphadenopathy)

- Kimura disease

- Toxoplasmosis

- Syphilis

- Castleman disease

- HIV-associated lymphadenopathy

- Progressive transformation of germinal centers (PTGC)