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.

Other symptoms of the syndrome include:

- retroorbital pain due to pain in the area supplied by the ophthalmic branch of the trigeminal nerve (fifth cranial nerve),

- abducens nerve palsy (sixth cranial nerve), and

- otitis media.

Other symptoms can include photophobia, excessive lacrimation, fever, and reduced corneal sensitivity.

The syndrome is usually caused by the spread of an infection into the petrous apex of the temporal bone.

Fever, sore throat, odynophagia (painful swallowing), swelling in neck.

In medicine, describing a disease as acute denotes that it is of short and, as a corollary of that, of recent . The quantitation of how much time constitutes "short" and "recent" varies by disease and by context, but the core denotation of "acute" is always qualitatively in contrast with "chronic", which denotes long-lasting disease (for example, in acute leukemia and chronic leukemia). In addition, "acute" also often connotes two other meanings: onset and , such as in acute myocardial infarction (EMI), where suddenness and severity are both established aspects of the meaning. It thus often connotes that the condition is fulminant (as in the EMI example), but not always (as in acute rhinitis, which is usually synonymous with the common cold). The one thing that acute MI and acute rhinitis have in common is that they are not chronic. They can happen again (as in recurrent pneumonia, that is, multiple acute pneumonia episodes), but they are not the same ongoing for months or years (unlike chronic obstructive pulmonary disease, which is).

A noncount sense of "acute disease" refers to the acute phase, that is, a short course, of any disease entity. For example, in an article on ulcerative enteritis in poultry, the author says, "in acute disease there may be increased mortality without any obvious signs", referring to the acute form or phase of ulcerative enteritis.

Gradenigo's syndrome, also called Gradenigo-Lannois syndrome and petrous apicitis, is a complication of otitis media and mastoiditis involving the apex of the petrous temporal bone. It was first described by Giuseppe Gradenigo in 1904 when he reported a triad of symptoms consisting of: (1)"unilateral periorbital pain" related to trigeminal nerve involvement, (2)"diplopia" due to sixth nerve palsy and (3)persistent "otorrhea", associated with bacterial otitis media with apex involvement of the petrous part of the temporal bone (petrositis). The classical syndrome related to otitis media has become very rare after the antibiotic era.

Patients with acute GPP experience the eruption of multiple isolated sterile pustules generalized over the body, recurrent fevers, fatigue, and laboratory abnormalities (elevated ESR, elevated CRP, combined with leukocytosis).

Anterior space abscess can cause trismus (spasm of jaw muscle) and hard mass formation along the angle of the mandible, with medial bulging of the tonsil and lateral pharyngeal wall. Posterior space abscess causes swelling in posterior pharyngeal wall. Trismus (spasm of jaw muscle) is minimal. Posterior abscess may involve structures within the carotid sheath, causing rigors, high fever, bacteremia, neurologic deficit, massive haemorrhage caused by carotid artery rupture.

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.

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

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.

Men with acute prostatitis often have chills, fever, pain in the lower back, perineum, or genital area, urinary frequency and urgency often at night, burning or painful urination, body aches, and a demonstrable infection of the urinary tract, as evidenced by white blood cells and bacteria in the urine. Acute prostatitis may be a complication of prostate biopsy. Often, the prostate gland is very tender to palpation through the rectum.

Symptomatic Hyperleukocytosis (Leukostasis) is defined by a tremendously high blast cell count along with symptoms of decreased tissue perfusion. Leukostasis is associated with people who suffer from bone and blood disorders and is very common among people suffering from acute myeloid leukemia or chronic myeloid leukemia. Leukostasis is a pathlogic diagnosis that inhibits efficient flow to the microvasculature of the body. Continued and untreated leukostasis presents respiratory and neurological distress simultaneously and is a medical emergency, with untreated patient mortality rates reaching a minimum of 20 and a maximum of 40 percent.. A leukemia blood cell count greater than 50 x 10^9/ L ((50,000 / microL) or 100 x 10^9 L / (100,000/ microL) signifies hyperleuckocytosis. Symptoms of leukostasis start when blood levels of leukocytes reach over 100 x 10^9 / L (100,000 / microL). As stated before, these counts are critical and associated with Leukemias.

AEN has never been recorded as a one symptom disorder, but instead present by multiple symptoms. The symptoms vary from the severity of the disorder. The most classic sign of AEN is the dark pigmentation of esophageal mucosa in an upper endoscopy, usually viewed as an ulcer or as an infectious disease. Necrosis can be found mostly between the three distals of the esophagus, but stops abruptly at the gastroesophageal junction. The basic and most common symptoms reported are blood in stool and blood in vomiting. Upper gastrointestinal bleeding then is reported, and is very commonly represented in elderly patients. Black or bloody stools and hematemesis account for over three quarters of the case presentations. Abdominal pain, nausea, vomiting, and unstable vital signs are common. A cardiovascular event (such as a heart attack) was reported in ten percent of the total known cases.

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).

Chest pain is one of the common symptoms of acute pericarditis. It is usually of sudden onset, occurring in the anterior chest and often has a sharp quality that worsens with breathing in or coughing, due to inflammation of the pleural surface at the same time. The pain may be reduced with sitting up and leaning forward while worsened with lying down, and also may radiate to the back, to one or both trapezius ridges. However, the pain can also be dull and steady, resembling the chest pain in an acute myocardial infarction. As with any chest pain, other causes must also be ruled out, such as GERD, pulmonary embolism, muscular pain, etc.

A pericardial friction rub is a very specific sign of acute pericarditis, meaning the presence of this sign invariably indicates presence of disease. However, absence of this sign does not rule out disease. This rub can be best heard by the diaphragm of the stethoscope at the left sternal border arising as a squeaky or scratching sound, resembling the sound of leather rubbing against each other. This sound should be distinguished from the sound of a murmur, which is similar but sounds more like a "swish" sound than a scratching sound. The pericardial rub is said to be generated from the friction generated by the two inflamed layers of the pericardium; however, even a large pericardial effusion does not necessarily present a rub. The rub is best heard during the maximal movement of the heart within the pericardial sac, namely, during atrial systole, ventricular systole, and the filling phase of early ventricular diastole.

Fever may be present since this is an inflammatory process.

Acute mast cell leukemia is a rapidly progressive disorder with leukemic mast cells in blood and in large numbers in marrow. The common signs and symptoms include fever, headache, flushing of face and trunk. The typical cutaneous mast cell infiltrates of urticaria pigmentosa are usually not present before, during, or after diagnosis in patients who have mast cell leukemia. Symptoms include abdominal pain, bone pain, and peptic ulcer which are more prevalent than in other subtypes of acute myeloid leukemia. These former symptoms are due to release of a substance called histamine from neoplastic mast cells. Enlargement of the liver and spleen, or hepatosplenomegaly is characteristic. The mast cells release also many anticoagulants like heparin which can lead to serious bleeding. Liver and splenic dysfunction also contributes to hemorrhage. Involvement of the bone can lead to osteoporosis. Abdominal ultrasound or computerized tomography (CT) scanning is used to look for hepatosplenomegaly and lymphadenopathy. Plain radiography and bone densitometry can be used to assess bone involvement and the presence of osteoporosis. Endoscopy and biopsy can be useful if gut involvement is suspected.

When a patient is suffering from symptomatic leuckocytosis, specifically caused by a form a leukemia, it is extremely common to find leukostasis in all their organs. The majority of the time a patient dies from neurological complications (40% of patients die due to neurological conditions) as opposed to particular organ damage. The lungs alone account for approximately 30 percent of leukostasis fatalities. All other organs combined attribute to 30 percent of deaths, with the major outliers being neurological and respiratory failure equating to 70 percent of all death rates. Damage to the microvasculature of the body is the primary cause of death by leukostasis. Microvasculatre damage to the lungs is only second to neurological damage because the body is already suffering from hypoxic conditions, which leads to lung tissue damage as the second leading cause of fatalities.

Pulmonary signs - Dyspnea and Hypoxia with or without diffuse interstitial or alveolar infiltrates on imaging studies.

Neurological signs - visual changes, headache, dizziness, tinnitus, gait instability, confusion, somnolence, coma.

The most common symptom is the patient is usually febrile, which is often linked with inflammation and possible infection.

Less common symptoms include electroencephalographic, signs of myocardial ischemia / right ventricular overload, increased renal insufficiency, priapism, acute limb ischemia and bowel infarction.

Mediastinitis is inflammation of the tissues in the mid-chest, or mediastinum. It can be either acute or chronic.

Acute mediastinitis is usually bacterial and due to rupture of organs in the mediastinum. As the infection can progress rapidly, this is considered a serious condition. Chronic sclerosing (or fibrosing) mediastinitis, while potentially serious, is caused by a long-standing inflammation of the mediastinum, leading to growth of acellular collagen and fibrous tissue within the chest and around the central vessels and airways. It has a different cause, treatment, and prognosis than acute infectious mediastinitis.

Space Infections : Pretracheal space - lies anterior to trachea. Pretracheal space infection leads to mediastinitis. Here, the fascia fuses with the pericardium and the parietal pleura , which explains the occurrence of empyema and pericardial effusion in mediastinitis.

Most initial symptoms of leukemia are similar to symptoms for irregular bone-marrow function. Typically, most symptoms do not occur during the early stages of leukemia, and children may experience different symptoms. The following are symptoms of leukemia that lead doctors to look for different types of juvenile leukemia:

The crisis is a common complication in sickle-cell patients and can be associated with one or more symptoms including fever, cough, excruciating pain, sputum production, shortness of breath, or low oxygen levels.

A specific histochemical reaction, cyanide-resistant peroxidase, permits identification of leukemic blast cells with eosinophilic differentiation and diagnosis of acute eosinoblastic leukemia in some cases of AML with few identifiable eosinophils in blood or marrow.

The most common symptoms of AEL are related to pancytopenia (a shortage of all types of blood cells), including fatigue, infections, and mucocutaneous bleeding. Almost half of people with AEL exhibit weight loss, fever and night sweats at the time of diagnosis. Almost all people with AEL are anemic, and 77% have a hemoglobin level under 10.0 g/dl. Signs of thrombocytopenia are found in about half of people with AEL.

Patients present with acute unilateral decreased vision, photopsias and central or paracentral scotoma. An antecedent viral prodrome occurs in approximately one-third of cases. Myopia is commonly seen in patients.

Eye exam during the acute phase of the disease reveals multiple discrete white to orange spots at the level of the RPE or deep retina, typically in a perifoveal location (around the fovea).

Acute chest syndrome is often precipitated by a lung infection, and the resulting inflammation and loss of oxygen saturation leads to further sickling of red cells, thus exacerbating pulmonary and systemic hypoxemia, sickling, and vaso-occlusion.

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.