Uremic pericarditis is correlated to the degree of azotemia in the system. BUN is normally >60 mg/dL (normal is 7–20 mg/dL). The pathogenesis is poorly understood.

Fibrinous pericarditis is an exudative inflammation. The pericardium is infiltrated by the fibrinous exudate. This consists of fibrin strands and leukocytes. Fibrin describes an amorphous, eosinophilic (pink) network. Leukocytes (white blood cells; mainly neutrophils) are found within the fibrin deposits and intrapericardic. Vascular congestion is also present. Inflammatory cells do not penetrate the myocardium (as is seen with other presentations of pericarditis), and as a result, this particular variant does not present with diffuse ST elevation on ECG (a classic sign of pericarditis known as stage I ECG changes which are seen with other causes). To naked eye examination, this pathology is referred to as having a "Bread and Butter Appearance".

If symptoms of histoplasmosis infection occur, they will start within 3 to 17 days after exposure; the average is 12–14 days. Most affected individuals have clinically silent manifestations and show no apparent ill effects. The acute phase of histoplasmosis is characterized by non-specific respiratory symptoms, often cough or flu-like. Chest X-ray findings are normal in 40–70% of cases. Chronic histoplasmosis cases can resemble tuberculosis; disseminated histoplasmosis affects multiple organ systems and is fatal unless treated.

While histoplasmosis is the most common cause of mediastinitis, this remains a relatively rare disease. Severe infections can cause hepatosplenomegaly, lymphadenopathy, and adrenal enlargement. Lesions have a tendency to calcify as they heal.

Presumed ocular histoplasmosis syndrome (POHS) causes chorioretinitis, where the choroid and retina of the eyes are scarred, resulting in a loss of vision not unlike macular degeneration. Despite its name, the relationship to "Histoplasma" is controversial. Distinct from POHS, acute ocular histoplasmosis may rarely occur in immunodeficiency.

In absence of proper treatment and especially in immunocompromised individuals, complications can arise. These include recurrent pneumonia, respiratory failure, fibrosing mediastinitis, superior vena cava syndrome, pulmonary vessel obstruction, progressive fibrosis of lymph nodes. Fibrosing mediastinitis is a serious complication and can be fatal. Smokers with structural lung disease have higher probability of developing chronic cavitary histoplasmosis.

After healing of lesions, hard calcified lymph nodes can erode the walls of airway causing hemoptysis.

Infective endocarditis may also be classified as "culture-positive" or "culture-negative". By far the most common cause of a "culture-negative" endocarditis is prior administration of antibiotics.

Sometimes microorganisms can take a longer period of time to grow in the culture media, such organisms are said to be "fastidious" because they have demanding growth requirements. Some examples include pathogens like "Aspergillus" species, "Brucella" species, "Coxiella burnetii", "Chlamydia" species, and HACEK bacteria. Due to delay in growth and identification in these cases, patients may be erroneously classified as "culture-negative" endocarditis.

Historically, infective endocarditis has been clinically divided into "acute" and "subacute" presentations (because untreated patients tended to live longer with the subacute as opposed to the acute form). This classifies both the rate of progression and severity of disease.

- "Subacute bacterial endocarditis" (SBE) is often due to streptococci of low virulence (mainly viridans streptococci) and mild to moderate illness which progresses slowly over weeks and months (>2 weeks) and has low propensity to hematogenously seed extracardiac sites.

- "Acute bacterial endocarditis" (ABE) is a fulminant illness over days to weeks (<2 weeks), and is more likely due to "Staphylococcus aureus" which has much greater virulence, or disease-producing capacity and frequently causes metastatic infection.

This classification is now discouraged, because the ascribed associations (in terms of organism and prognosis) were not strong enough to be relied upon clinically. The terms "short incubation" (meaning less than about six weeks), and "long incubation" (greater than about six weeks) are preferred.

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.

The signs and symptoms of Lemierre's syndrome vary, but usually start with a sore throat, fever, and general body weakness. These are followed by extreme lethargy, spiked fevers, rigors, swollen cervical lymph nodes, and a swollen, tender or painful neck. Often there is abdominal pain, diarrhea, nausea and vomiting during this phase. These signs and symptoms usually occur several days to 2 weeks after the initial symptoms.

Symptoms of pulmonary involvement can be shortness of breath, cough and painful breathing (pleuritic chest pain). Rarely, blood is coughed up. Painful or inflamed joints can occur when the joints are involved.

Septic shock can also arise. This presents with low blood pressure, increased heart rate, decreased urine output and an increased rate of breathing. Some cases will also present with meningitis, which will typically manifest as neck stiffness, headache and sensitivity of the eyes to light.

Liver enlargement and spleen enlargement can be found, but are not always associated with liver or spleen abscesses.

Other signs and symptoms that may occur:

- Headache (unrelated to meningitis)

- Memory loss

- Muscle pain

- Jaundice

- Decreased ability to open the jaw

- Crepitations are sometimes heard over the lungs

- Pericardial friction rubs as a sign of pericarditis (rare)

- Cranial nerve paralysis and Horner's syndrome (both rare)

Pericarditis can progress to pericardial effusion and eventually cardiac tamponade. This can be seen in patients who are experiencing the classic signs of pericarditis but then show signs of relief, and progress to show signs of cardiac tamponade which include decreased alertness and lethargy, pulsus paradoxus (decrease of at least 10 mmHg of the systolic blood pressure upon inspiration), low blood pressure (due to decreased cardiac index), (jugular vein distention from right sided heart failure and fluid overload), distant heart sounds on auscultation, and equilibration of all the diastolic blood pressures on cardiac catheterization due to the constriction of the pericardium by the fluid.

In such cases of cardiac tamponade, EKG or Holter monitor will then depict electrical alternans indicating wobbling of the heart in the fluid filled pericardium, and the capillary refill might decrease, as well as severe vascular collapse and altered mental status due to hypoperfusion of body organs by a heart that can not pump out blood effectively.

The diagnosis of tamponade can be confirmed with trans-thoracic echocardiography (TTE), which should show a large pericardial effusion and diastolic collapse of the right ventricle and right atrium. Chest X-ray usually shows an enlarged cardiac silhouette ("water bottle" appearance) and clear lungs. Pulmonary congestion is typically not seen because equalization of diastolic pressures constrains the pulmonary capillary wedge pressure to the intra-pericardial pressure (and all other diastolic pressures).

The classic sign of pericarditis is a friction rub heard with a stethoscope on the cardiovascular examination usually on the lower left sternal border. Other physical signs include a patient in distress, positional chest pain, diaphoresis (excessive sweating), and possibility of heart failure in form of pericardial tamponade causing pulsus paradoxus, and the Beck's triad of low blood pressure (due to decreased cardiac output), distant (muffled) heart sounds, and distension of the jugular vein (JVD).

Signs and symptoms of PCP include fever, non-productive cough (because sputum is too viscous to become productive), shortness of breath (especially on exertion), weight loss, and night sweats. There is usually not a large amount of sputum with PCP unless the patient has an additional bacterial infection. The fungus can invade other visceral organs (such as the liver, spleen, and kidney), but only in a minority of cases.

Pneumothorax is a well-known complication of PCP. An acute history of chest pain with breathlessness and diminished breath sounds is typical of pneumothorax.

"Pneumocystis" pneumonia (PCP) is a form of pneumonia, caused by the yeast-like fungus "Pneumocystis jirovecii".

"Pneumocystis" pneumonia is not commonly found in the lungs of healthy people, but, being a source of opportunistic infection, it can cause a lung infection in people with a weak immune system. "Pneumocystis" pneumonia is especially seen in people with cancer undergoing chemotherapy, HIV/AIDS, and the use of medications that suppress the immune system.

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

Tuberculous pericarditis is a form of pericarditis.

Pericarditis caused by tuberculosis is difficult to diagnose, because definitive diagnosis requires culturing "Mycobacterium tuberculosis" from aspirated pericardial fluid or pericardial , which requires high technical skill and is often not diagnostic (the yield from culture is low even with optimum specimens). The Tygerberg scoring system helps the clinician to decide whether pericarditis is due to tuberculosis or whether it is due to another cause: night sweats (1 point), weight loss (1 point), fever (2 point), serum globulin > 40g/l (3 points), blood total leucocyte count <10 x 10/l (3 points); a total score of 6 or more is highly suggestive of tuberculous pericarditis. Pericardial fluid with an interferon-γ level greater than 50/ml is highly specific for tuberculous pericarditis.

There are no randomized trials which evaluate the length of anti-tuberculosis treatment required for tuberculous pericarditis. There is a small but not conclusive benefit for treatment with a schedule of steroids with anti-tuberculosis drugs. Open surgical drainage of fluid though effective in preventing cardiac tamponade was associated with more deaths.

Signs and symptoms of constrictive pericarditis are consistent with the following: fatigue, swollen abdomen, difficulty breathing (dyspnea), swelling of legs and general weakness. Related conditions are bacterial pericarditis, pericarditis and pericarditis after a heart attack.

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.

Lemierre's syndrome (or Lemierre's disease, also known as postanginal shock including sepsis and human necrobacillosis) refers to infectious thrombophlebitis of the internal jugular vein. It most often develops as a complication of a bacterial sore throat infection in young, otherwise healthy adults. The thrombophlebitis is a serious condition and may lead to further systemic complications such as bacteria in the blood or septic emboli.

Lemierre's syndrome occurs most often when a bacterial (e.g., "Fusobacterium necrophorum") throat infection progresses to the formation of a peritonsillar abscess. Deep in the abscess, anaerobic bacteria can flourish. When the abscess wall ruptures internally, the drainage carrying bacteria seeps through the soft tissue and infects the nearby structures. Spread of infection to the nearby internal jugular vein provides a gateway for the spread of bacteria through the bloodstream. The inflammation surrounding the vein and compression of the vein may lead to blood clot formation. Pieces of the potentially infected clot can break off and travel through the right heart into the lungs as emboli, blocking branches of the pulmonary artery that carry blood with little oxygen from the right side of the heart to the lungs.

Sepsis following a throat infection was described by Schottmuller in 1918. However, it was André Lemierre, in 1936, who published a series of 20 cases where throat infections were followed by identified anaerobic sepsis, of whom 18 patients died.

The defining symptom of pleurisy is a sudden sharp, stabbing, burning or dull pain in the right or left side of the chest during breathing, especially when one inhales and exhales. It feels worse with deep breathing, coughing, sneezing, or laughing. The pain may stay in one place, or it may spread to the shoulder or back. Sometimes, it becomes a fairly constant dull ache.

Depending on its cause, pleuritic chest pain may be accompanied by other symptoms:

- Dry cough

- Fever and chills

- Rapid, shallow breathing

- Shortness of breath

- Fast heart rate

- Sore throat followed by pain and swelling in the joints

The vegetations are small and formed from strands of fibrin, neutrophils, lymphocytes, and histiocytes. The mitral valve is typically affected, and the vegetations occur on the ventricular and atrial surface of the valve. Libman–Sacks lesions rarely produce significant valve dysfunction and the lesions only rarely embolize. However, there is data to suggest an association between Libman–Sacks endocarditis and a higher risk for embolic cerebrovascular disease in people with systemic lupus erythematosus (SLE).

The pathology is the same as nonbacterial thrombotic endocarditis except focal necrosis with hematoxylin bodies can be found only in Libman–Sacks endocarditis.

The cause of constrictive pericarditis in the developing world are idiopathic in origin, though likely infectious in nature. In regions where tuberculosis is common, it is the cause in a large portion of cases.

Causes of constrictive pericarditis include:

- Tuberculosis

- Incomplete drainage of purulent pericarditis

- Fungal and parasitic infections

- Chronic pericarditis

- Postviral pericarditis

- Postsurgical

- Following MI, post-myocardial infarction

- In association with pulmonary asbestos

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".

Pleurisy, also known as pleuritis, is inflammation of the membranes (pleurae) that surround the lungs and line the chest cavity. This can result in a sharp chest pain with breathing. Occasionally the pain may be a constant dull ache. Other symptoms may include shortness of breath, cough, fever, or weight loss depending on the underlying cause.

The most common cause is a viral infection. Other causes include pneumonia, pulmonary embolism, autoimmune disorders, lung cancer, following heart surgery, pancreatitis, chest trauma, and asbestosis. Occasionally the cause remains unknown. The underlying mechanism involves the rubbing together of the pleurae instead of smooth gliding. Other conditions that can produce similar symptoms include pericarditis, heart attack, cholecystitis, and pneumothorax. Diagnosis may include a chest X-ray, electrocardiogram (ECG), and blood tests.

Treatment depends on the underlying cause. Paracetamol and ibuprofen may be used to help with the pain. Incentive spirometry may be recommended to encourage larger breaths. About one million people are affected in the United States each year. Descriptions of the condition date from at least as early as 400 BC by Hippocrates.

Fungal meningitis refers to meningitis caused by a fungal infection.

Progressive disseminated histoplasmosis is an infection caused by Histoplasma capsulatum, and most people who develop this severe form of histoplasmosis are immunocompromised or taking systemic corticosteroids. Skin lesions are present in approximately 6% of patients with dissemination.