Perichondritis is inflammation of the perichondrium, a layer of connective tissue which surrounds cartilage. A common form, auricular perichondritis ("perichondritis auriculae") involves infection of the pinna due to infection of traumatic or surgical wound or the spread of inflammation into depth. It may lead to severe deformation of the pinna if not treated vigorously with IV antibiotics. The causative organism is usually "Pseudomonas aeruginosa". A rare form is laryngeal perichondritis ("perichondritis laryngis"). It develops suddenly due to an injury, virulent organisms or compromised immune status of the host, and also affects cartilage of the larynx. This may result in deformations and stenoses.

Many individuals have mild symptoms, which recur infrequently, while others may have persistent problems that become debilitating or life-threatening.

Relapsing polychondritis is an autoimmune disease in which the body's immune system begins to attack and destroy the cartilage tissues in the body. It has been postulated that both cell-mediated immunity and humoral immunity are responsible.

Reasons for disease onset are not known, but there is no evidence of a genetic predisposition to developing relapsing polychondritis. However, there are cases where multiple members of the same family have been diagnosed with this illness. Studies indicate that some genetic contribution to susceptibility is likely.

Long-term antibiotics, while they decrease rates of infection during treatment, have an unknown effect on long-term outcomes such as hearing loss. This method of prevention has been associated with emergence of antibiotic-resistant otitic bacteria. They are thus not recommended.

Pneumococcal conjugate vaccines (PCV) in early infancy, decreases the risk of acute otitis media in healthy infants. PCV is recommended for all children, and, if implemented broadly, PCV would have a significant public health benefit. Influenza vaccine is recommended annually for all children. PCV does not appear to decrease the risk of otitis media when given to high-risk infants or for older children who have previously experienced otitis media.

Risk factors such as season, allergy predisposition and presence of older siblings are known to be determinants of recurrent otitis media and persistent middle-ear effusions (MEE). History of recurrence, environmental exposure to tobacco smoke, use of daycare, and lack of breastfeeding have all been associated with increased risk of development, recurrence, and persistent MEE. Thus, cessation of smoking in the home should be encouraged, daycare attendance should be avoided or daycare facilities with the fewest attendees should be recommended, and breastfeeding should be promoted.

There is some evidence that breastfeeding for the first year of life is associated with a reduction in the number and duration of OM infections. Pacifier use, on the other hand, has been associated with more frequent episodes of AOM.

Evidence does not support zinc supplementation as an effort to reduce otitis rates except maybe in those with severe malnutrition such as marasmus.

Adhesive otitis media occurs when a thin retracted ear drum becomes sucked into the middle-ear space and stuck (i.e., adherent) to the ossicles and other bones of the middle ear.

Laryngitis that continues for more than three weeks is considered chronic. If laryngeal symptoms last for more than three weeks, a referral should be made for further examination, including direct laryngoscopy. The prognosis for chronic laryngitis varies depending on the cause of the laryngitis.

The Appaloosa has a higher risk of developing ERU than other breeds; this predisposition has a genetic basis. Appaloosas which develop ERU are more likely than other breeds to have ERU in both eyes, and more likely to become blind in one or both eyes.

Several aetiologies are suggested, and any combination of these may be present in any given case.

- Vitamin deficiency (A, B or C)

- Viral infection

- Bacterial infection

- "Leptospira

- "Streptococcus

- "Brucella

- Parasitic infection

- Strongyle

- "Onchocerca cervicalis"

- Autoimmune disease

The disease has been suggested to be primarily autoimmune in nature, being a delayed hypersensitivity reaction to any of the above agents.

There are several causes of acute pericarditis. In developed nations, the cause of most (80–90%) cases of acute pericarditis is unknown but a viral cause is suspected in the majority of such cases. The other 10–20% of acute pericarditis cases have various causes including connective tissue diseases (e.g., systemic lupus erythematosus), cancer, or involve an inflammatory reaction of the pericardium following trauma to the heart such as after a heart attack such as Dressler's syndrome. Familial mediterranean fever and TNF receptor associated periodic syndrome are rare inherited autoimmune diseases capable of causing recurring episodes of acute pericarditis.

Acute laryngitis may persist, but will typically resolve on its own within two weeks. Recovery is likely to be quick if the patient follows the treatment plan. In viral laryngitis, symptoms can persist for an extended amount of time, even when upper respiratory tract inflammation has been resolved.

Having cancer (current or previous) is currently one of the most prevalent out of all conditions among patients. High blood pressure, Chronic lung conditions, Alcohol abuse, Kidney failure, Malnutrition are another major risk factors.

von Zumbusch (acute) generalized pustular psoriasis, (acute GPP) is the most severe form of generalized pustular psoriasis, and can be associated with life-threatening complications.

Chronic mediastinitis is usually a radiologic diagnosis manifested by diffuse fibrosis of the soft tissues of the mediastinum. This is sometimes the consequence of prior granulomatous disease, most commonly histoplasmosis. Other identifiable causes include tuberculosis, IgG4-related disease and radiation therapy. Fibrosing mediastinitis most frequently causes problems by constricting blood vessels or airways in the mediastinum. This may result in such complications as superior vena cava syndrome or pulmonary edema from compression of pulmonary veins.

Treatment for chronic fibrosing mediastinitis is somewhat controversial, and may include steroids or surgical decompression of affected vessels.

Acute esophageal necrosis made an appearance on an American medical drama show, . Jan Garavaglia, the show's host, receives a female body, that at time of the autopsy had a severe case of acute esophageal necrosis due to chronic alcoholism.

Before the development of modern cardiovascular surgery, cases of acute mediastinitis usually arose from either perforation of the esophagus or from contiguous spread of odontogenic or retropharyngeal infections. However, in modern practice, most cases of acute mediastinitis result from complications of cardiovascular or endoscopic surgical procedures.

Treatment usually involves aggressive intravenous antibiotic therapy and hydration. If discrete fluid collections or grossly infected tissue have formed (such as abscesses), they may have to be surgically drained or debrided.

Acute GPP typically requires inpatient management including both topical and systemic therapy, and supportive measures. Systemic glucocorticoid withdrawal is a common causative agent. Withdrawal or administration of certain drugs in the patient's previous medication regimen may be required. Oral retinoids are the most effective treatment, and are considered first line. Cyclosporine or infliximab may be required for particularly acute cases.

Treatment is symptomatic, often addressing indicators associated with peripheral pulmonary artery stenosis. Laryngotracheal calcification resulting in dyspnea and forceful breathing can be treated with bronchodilators including the short and long-acting β2-agonists, and various anticholinergics. Prognosis is good, yet life expectancy depends on the severity and extent of diffuse pulmonary and arterial calcification.

Acute care is the early and specialist management of adult patients suffering from a wide range of medical conditions requiring urgent or emergency care usually within 48 hoursof admission or referral from other specialties.

Acute hospitals are those intended for short-term medical and/or surgical treatment and care. The related medical speciality is acute medicine.

Not all acute diseases or injuries are severe, and vice versa. For example, a mild stubbed toe is an acute injury. Similarly, many acute upper respiratory infections and acute gastroenteritis cases in adults are mild and usually resolve within a few days or weeks.

The term "acute" is also included in the definition of several diseases, such as severe acute respiratory syndrome, acute leukemia, acute myocardial infarction, and acute hepatitis. This is often to distinguish diseases from their chronic forms, such as chronic leukemia, or to highlight the sudden onset of the disease, such as acute myocardial infarct.

Clinical presentation of diseases of pericardium may vary between:

- Acute and recurrent pericarditis

- Pericardial effusion without major hemodynamic compromise

- Cardiac tamponade

- Constrictive pericarditis

- Effusive-constrictive pericarditis

Acute cerebellar ataxia is the most common cause of unsteady gait in children. The condition is rare in children older than ten years of age. Most commonly acute cerebellar ataxia affects children between age 2 and 7 years.

The major cause of acute limb ischaemia is arterial thrombosis (85%), while embolic occlusion is responsible for 15% of cases. In rare instances, arterial aneurysm of the popliteal artery has been found to create a thrombosis or embolism resulting in ischaemia.

In the United States, the annual incidence is 18 cases of acute pancreatitis per 100,000 population, and it accounts for 220,000 hospitalizations in the US. In a European cross-sectional study, incidence of acute pancreatitis increased from 12.4 to 15.9 per 100,000 annually from 1985 to 1995; however, mortality remained stable as a result of better outcomes. Another study showed a lower incidence of 9.8 per 100,000 but a similar worsening trend (increasing from 4.9 in 1963-74) over time.

In Western countries, the most common cause is alcohol, accounting for 65 percent of acute pancreatitis cases in the US, 20 percent of cases in Sweden, and 5 percent of those in the United Kingdom. In Eastern countries, gallstones are the most common cause of acute pancreatitis. The causes of acute pancreatitis also varies across age groups, with trauma and systemic disease (such as infection) being more common in children. Mumps is a more common cause in adolescents and young adults than in other age groups.

It may result in death, and it is one of the most common causes of death for people with sickle cell anemia.

Acute prostatitis is a serious bacterial infection of the prostate gland. This infection is a medical emergency. It should be distinguished from other forms of prostatitis such as chronic bacterial prostatitis and chronic pelvic pain syndrome (CPPS).