In Yorkshire Terriers there can be severe mononuclear inflammation of the brainstem and periventricular cerebral white matter. Because the condition in this breed frequently affects only the white matter, it has been called necrotizing leukoencephalitis. Symptoms of brainstem and central vestibular disease predominate.

Granulomatous meningoencephalitis (GME) is an inflammatory disease of the central nervous system (CNS) of dogs and, rarely, cats. It is a form of meningoencephalitis. GME is likely second only to encephalitis caused by "canine distemper virus" as the most common cause of inflammatory disease of the canine CNS. The disease is more common in female toy dogs of young and middle age. It has a rapid onset. The lesions of GME exist mainly in the white matter of the cerebrum, brainstem, cerebellum, and spinal cord. The cause is only known to be noninfectious and is considered at this time to be idiopathic. Because lesions resemble those seen in allergic meningoencephalitis, GME is thought to have an immune-mediated cause, but it is also thought that the disease may be based on an abnormal response to an infectious agent. One study searched for viral DNA from "canine herpesvirus", "canine adenovirus", and "canine parvovirus" in brain tissue from dogs with GME, necrotizing meningoencephalitis, and necrotizing leukoencephalitis (see below for the latter two conditions), but failed to find any.

Phlegmon is a spreading diffuse inflammatory process with formation of purulent exudate (the suppuration of pus). This is the result of acute purulent inflammation which may be related to bacterial infection; however, the term 'phlegmon' (from Greek 'phlegmone', inflammation) mostly refers to a walled-off inflammatory mass without bacterial infection, one that may be palpable on physical examination.

An example would be phlegmon of diverticulitis. In this case a patient would present to the emergency department with left lower-quadrant abdominal tenderness, and the diagnosis of sigmoid diverticulitis would be high on the differential diagnosis, yet the best test to confirm it would be CT scan.

Another example, phlegmon affecting the spine, is known as spondylodiscitis and is associated with endplate destruction and loss of disc height. In adults, the bone marrow is affected first, while in children, the disease starts in the disc itself and spreads rapidly to the adjacent vertebral bodies. Phlegmon in the spine can be a diffuse enhancement, or localized abscess, (peripheral enhancement) in the epidural, subligamentous or paraspinous spaces. Under MRI examination, phlegmon will show dark with T1, and high signal (bright) with T2.

Meningeal syphilis (as known as syphilitic aseptic meningitis or meningeal neurosyphilis) is a chronic form of syphilis infection that affects the central nervous system. Treponema pallidum, which is a spirochate bacterium, is the main cause of syphilis, which spreads drastically throughout the body and can infect all the systems of the body if not treated appropriately. The bacterium is the main cause of the onset of meningeal syphilis and other treponemal diseases, and it consists of a cytoplasmic and outer membrane that can cause a diverse array of diseases in the central nervous system and brain.

Early symptomatic neurosyphillis (or acute syphilitic meningitis or neurorecurrence) is the onset of meningeal syphilis. The symptoms arise as a result of inflamed meninges, which eventually lead up to signs of meningitis.

"Treponema pallidum" invades the nervous system within three to eighteen months after the primary infection. The initial series of events is asymptomatic meningitis, which can remain in the human body system and produce more damage within the body. Every form of neurosyphilis has meningitis as a component; however, every case differs in severity. The individual is infected with syphilis through a gram negative bacteria that only humans can obtain. Syphilis has four stages of infection, which are primary, secondary, latent, and tertiary. If syphilis is not treated, the disease can affect various other systems in the body, including the brain, heart, and vessels. The infection of the heart and vessels leads to meningovascular syphilis, which is usually presented during the secondary stage of syphilis. If syphilis is prolonged, it can affect the nervous system, which is known as neurosyphilis. Meningeal syphilis is a component of neurosyphilis, which usually occurs in the tertiary stage of syphilis.

Systemic features of infection such as increased body temperature (up to 38-40 °C), general fatigue, chills, sweatings, headache, loss of appetite).

Inflammatory signs – dolor (localized pain), calor (increase local tissue temperature), rubor (skin redness/hyperemia), tumor (either clear or non-clear bordered tissue swelling), functio laesa (diminish affected function).

NB: severity of patient condition with phlegmons is directly proportional to the degree of intoxication level i.e. the more severe the condition, the higher the degree of intoxication level.

A noninfectious occurrence of phlegmon can be found in the acute pancreatitis of Systemic Lupus Erythematosus. The immunosuppressive aspects of this disease and the immunosuppressive medications used to treat it blunt each of the signs of infection.

Swelling may be severe enough to put pressure on the eye and distort vision. Some patients first thought to have dacryoadenitis may turn out to have a malignancy of the lacrimal gland.

Arachnoiditis is a chronic disorder with no known cure, and prognosis may be hard to determine because of an unclear correlation between the beginning of the disease and the appearance of symptoms. For many, arachnoiditis is a disabling disease that causes chronic pain and neurological deficits, and may also lead to other spinal cord conditions, such as syringomyelia.

Dacryoadenitis is inflammation of the lacrimal glands (the tear-producing glands).

The types of neurosyphilis include asymptomatic, acute syphilitic meningitis, meningovascular syphilis, parenchymatous syphilis (which includes general paresis and tabes dorsalis), and optic atrophy.

For the ossificans form of the condition, unenhanced CT may better show the presence and extent of arachnoid ossifications, and is complementary to MRI, as MRI can be less specific and findings can be confused with regions of calcification or hemosiderin.

Tenosynovitis is the inflammation of the fluid-filled sheath (called the synovium) that surrounds a tendon, typically leading to joint pain, swelling, and stiffness. Tenosynovitis can be either infectious or noninfectious. Common clinical manifestations of noninfectious tenosynovitis include de Quervain tendinopathy and stenosing tenosynovitis (more commonly known as trigger finger)

The most common manifestation of infectious tenosynovitis is in the flexor tendons of the fingers, though infections of other tendon sheaths have been reported as well. The four cardinal signs of infectious flexor tenosynovitis are tenderness to touch along the flexor aspect of the finger, symmetric enlargement of the affected finger, the finger being held in slight flexion at rest, and severe pain with passive extension. Fever may also be present but is uncommon.

Urethritis is inflammation of the urethra. The most common symptom is painful or difficult urination. It is usually caused by infection with bacteria. The bacterial infection is often sexually transmitted, but not in every instance. Urethritis can be idiopathic.

The primary symptom of laryngitis is a hoarse voice. Because laryngitis can have various causes, other signs and symptoms may vary. They can include

- Dry or sore throat

- Coughing (both a causal factor and a symptom of laryngitis)

- Frequent throat clearing

- Increased saliva production

- Dysphagia (difficulty swallowing)

- Sensation of swelling in the area of the larynx (discomfort in the front of the neck)

- Globus pharyngeus (feeling like there is a lump in the throat)

- Cold or flu-like symptoms (which, like a cough, may also be a causal factor for laryngitis)

- Swollen lymph nodes in the throat, chest, or face

- Fever

- General muscle pain (myalgia)

- Shortness of breath, predominantly in children

SIRS is frequently complicated by failure of one or more organs or organ systems. The complications of SIRS include:

- Acute lung injury

- Acute kidney injury

- Shock

- Multiple organ dysfunction syndrome

Aside from a hoarse-sounding voice, changes to pitch and volume may occur with laryngitis. Speakers may experience a lower or higher pitch than normal, depending on whether their vocal folds are swollen or stiff. They may also have breathier voices, as more air flows through the space between the vocal folds (the glottis), quieter volume and a reduced range.

People with infectious pneumonia often have a productive cough, fever accompanied by shaking chills, shortness of breath, sharp or stabbing chest pain during deep breaths, and an increased rate of breathing. In the elderly, confusion may be the most prominent sign.

The typical signs and symptoms in children under five are fever, cough, and fast or difficult breathing. Fever is not very specific, as it occurs in many other common illnesses, may be absent in those with severe disease, malnutrition or in the elderly. In addition, a cough is frequently absent in children less than 2 months old. More severe signs and symptoms in children may include blue-tinged skin, unwillingness to drink, convulsions, ongoing vomiting, extremes of temperature, or a decreased level of consciousness.

Bacterial and viral cases of pneumonia usually present with similar symptoms. Some causes are associated with classic, but non-specific, clinical characteristics. Pneumonia caused by "Legionella" may occur with abdominal pain, diarrhea, or confusion, while pneumonia caused by "Streptococcus pneumoniae" is associated with rusty colored sputum, and pneumonia caused by "Klebsiella" may have bloody sputum often described as "currant jelly". Bloody sputum (known as hemoptysis) may also occur with tuberculosis, Gram-negative pneumonia, and lung abscesses as well as more commonly with acute bronchitis. "Mycoplasma" pneumonia may occur in association with swelling of the lymph nodes in the neck, joint pain, or a middle ear infection. Viral pneumonia presents more commonly with wheezing than does bacterial pneumonia. Pneumonia was historically divided into "typical" and "atypical" based on the belief that the presentation predicted the underlying cause. However, evidence has not supported this distinction, thus it is no longer emphasized.

Systemic inflammatory response syndrome (SIRS) is an inflammatory state affecting the whole body. It is the body's response to an infectious or noninfectious insult. Although the definition of SIRS refers to it as an "inflammatory" response, it actually has pro- and anti-inflammatory components.

Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli. Typically symptoms include some combination of productive or dry cough, chest pain, fever, and trouble breathing. Severity is variable.

Pneumonia is usually caused by infection with viruses or bacteria and less commonly by other microorganisms, certain medications and conditions such as autoimmune diseases. Risk factors include other lung diseases such as cystic fibrosis, COPD, and asthma, diabetes, heart failure, a history of smoking, a poor ability to cough such as following a stroke, or a weak immune system. Diagnosis is often based on the symptoms and physical examination. Chest X-ray, blood tests, and culture of the sputum may help confirm the diagnosis. The disease may be classified by where it was acquired with community, hospital, or health care associated pneumonia.

Vaccines to prevent certain types of pneumonia are available. Other methods of prevention include handwashing and not smoking. Treatment depends on the underlying cause. Pneumonia believed to be due to bacteria is treated with antibiotics. If the pneumonia is severe, the affected person is generally hospitalized. Oxygen therapy may be used if oxygen levels are low.

Pneumonia affects approximately 450 million people globally (7% of the population) and results in about 4 million deaths per year. Pneumonia was regarded by William Osler in the 19th century as "the captain of the men of death". With the introduction of antibiotics and vaccines in the 20th century, survival improved. Nevertheless, in developing countries, and among the very old, the very young, and the chronically ill, pneumonia remains a leading cause of death. Pneumonia often shortens suffering among those already close to death and has thus been called "the old man's friend".

The disease is classified as either gonococcal urethritis, caused by "Neisseria gonorrhoeae", or non-gonococcal urethritis (NGU), most commonly caused by "Chlamydia trachomatis". NGU, sometimes called nonspecific urethritis (NSU), has both infectious and noninfectious causes.

Urethritis is part of triad of Reiter's Syndrome.

Other causes include:

- Adenoviridae

- Uropathogenic "Escherichia coli" (UPEC)

- Herpes simplex

- Cytomegalovirus

- "Mycoplasma genitalium"

- Reactive arthritis

- "Trichomonas vaginalis"

- "Ureaplasma urealyticum"

- "Methicillin-resistant Staphylococcus aureus"

- "Group B streptococcus"

Idiopathic interstitial pneumonia (IIP), or noninfectious pneumonia are a class of diffuse lung diseases. These diseases typically affect the pulmonary interstitium, although some also have a component affecting the airways (for instance, Cryptogenic organizing pneumonitis). There are seven recognized distinct subtypes of IIP.

Classification can be complex, and the combined efforts of clinicians, radiologists, and pathologists can help in the generation of a more specific diagnosis.

Idiopathic interstitial pneumonia can be subclassified based on histologic appearance into the following patterns:

Usual interstitial pneumonia is the most common type.

The differential diagnosis for sepsis is broad and has to examine (to exclude) the noninfectious conditions that may cause the systemic signs of SIRS: alcohol withdrawal, acute pancreatitis, burns, pulmonary embolism, thyrotoxicosis, anaphylaxis, adrenal insufficiency, and neurogenic shock. Hyperinflammatory syndromes such as hemophagocytic lymphohistiocytosis (HLH) may have similar symptoms and should also be included in differential diagnosis.

The symptoms of CVID vary between people affected. Its main features are hypogammaglobulinemia and recurrent infections. Hypogammaglobulinemia manifests as a significant decrease in the levels of IgG antibodies, usually alongside IgA antibodies; IgM antibody levels are also decreased in about half of people. Infections are a direct result of the low antibody levels in the circulation, which do not adequately protect them against pathogens. The microorganisms that most frequently cause infections in CVID are bacteria Haemophilus influenzae, Streptococcus pneumoniae and Staphylococcus aureus. Pathogens less often isolated from people include Neisseria meningitidis, Pseudomonas aeruginosa and Giardia lamblia. Infections mostly affect the respiratory tract (nose, sinuses, bronchi, lungs) and the ears; they can also occur at other sites, such as the eyes, skin and gastrointestinal tract. These infections respond to antibiotics but can recur upon discontinuation of antibiotics. Bronchiectasis can develop when severe, recurrent pulmonary infections are left untreated.

In addition to infections, people with CVID can develop complications. These include:

- autoimmune manifestations, e.g. pernicious anemia, autoimmune haemolytic anemia (AHA), idiopathic thrombocytopenic purpura (ITP), psoriasis, vitiligo, rheumatoid arthritis, primary hypothyroidism, atrophic gastritis. Autoimmunity is the main type of complication in people with CVID, appearing in some form in up to 50% of individuals;

- malignancies, particularly Non-Hodgkin's lymphoma and gastric carcinoma;

- enteropathy, which manifests with a blunting of intestinal villi and inflammation, and is usually accompanied by symptoms such as abdominal cramps, diarrhea, constipation and, in some cases, malabsorption and weight loss. Symptoms of CVID enteropathy are similar to those of celiac disease, but don't respond to a gluten-free diet. Infectious causes must be excluded before a diagnosis of enteropathy can be made, as people with CVID are more susceptible to intestinal infections, e.g. by Giardia lamblia;

- lymphocytic infiltration of tissues, which can cause enlargement of lymph nodes (lymphadenopathy), of the spleen (splenomegaly) and of the liver (hepatomegaly), as well as the formation of granulomas. In the lung this is known as Granulomatous–lymphocytic interstitial lung disease.

Anxiety and depression can occur as a result of dealing with the other symptoms.

People generally complain of severe fatigue.

Sepsis is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. Common signs and symptoms include fever, increased heart rate, increased breathing rate, and confusion. There also may be symptoms related to a specific infection, such as a cough with pneumonia, or painful urination with a kidney infection. In the very young, old, and people with a weakened immune system, there may be no symptoms of a specific infection and the body temperature may be low or normal, rather than high. Severe sepsis is sepsis causing poor organ function or insufficient blood flow. Insufficient blood flow may be evident by low blood pressure, high blood lactate, or low urine output. Septic shock is low blood pressure due to sepsis that does not improve after reasonable amounts of intravenous fluids are given.

Sepsis is caused by an immune response triggered by an infection. Most commonly, the infection is bacterial, but it may also be from fungi, viruses, or parasites. Common locations for the primary infection include lungs, brain, urinary tract, skin, and abdominal organs. Risk factors include young or old age, a weakened immune system from conditions such as cancer or diabetes, major trauma, or burns. An older method of diagnosis was based on meeting at least two systemic inflammatory response syndrome (SIRS) criteria due to a presumed infection. In 2016, SIRS was replaced with qSOFA which is two of the following three: increased breathing rate, change in level of consciousness, and low blood pressure. Blood cultures are recommended preferably before antibiotics are started, however, infection of the blood is not required for the diagnosis. Medical imaging should be used to look for the possible location of infection. Other potential causes of similar signs and symptoms include anaphylaxis, adrenal insufficiency, low blood volume, heart failure, and pulmonary embolism, among others.

Sepsis usually is treated with intravenous fluids and antibiotics. Typically, antibiotics are given as soon as possible. Often, ongoing care is performed in an intensive care unit. If fluid replacement is not enough to maintain blood pressure, medications that raise blood pressure may be used. Mechanical ventilation and dialysis may be needed to support the function of the lungs and kidneys, respectively. To guide treatment, a central venous catheter and an arterial catheter may be placed for access to the bloodstream. Other measurements such as cardiac output and superior vena cava oxygen saturation may be used. People with sepsis need preventive measures for deep vein thrombosis, stress ulcers and pressure ulcers, unless other conditions prevent such interventions. Some might benefit from tight control of blood sugar levels with insulin. The use of corticosteroids is controversial. Activated drotrecogin alfa, originally marketed for severe sepsis, has not been found to be helpful, and was withdrawn from sale in 2011.

Disease severity partly determines the outcome. The risk of death from sepsis is as high as 30%, from severe sepsis as high as 50%, and from septic shock as high as 80%. The number of cases worldwide is unknown as there is little data from the developing world. Estimates suggest sepsis affects millions of people a year. In the developed world approximately 0.2 to 3 people per 1000 are affected by sepsis yearly, resulting in about a million cases per year in the United States. Rates of disease have been increasing. Sepsis is more common among males than females. The medical condition has been described since the time of Hippocrates. Septicemia and blood poisoning are terms that referred to the microorganisms or their toxins in the blood and are no longer commonly used.