The signs and symptoms associated with myocarditis are varied, and relate either to the actual inflammation of the myocardium or to the weakness of the heart muscle that is secondary to the inflammation. Signs and symptoms of myocarditis include the following:

- Chest pain (often described as "stabbing" in character)

- Congestive heart failure (leading to swelling, shortness of breath and liver congestion)

- Palpitations (due to abnormal heart rhythms)

- Sudden death (in young adults, myocarditis causes up to 20% of all cases of sudden death)

- Fever (especially when infectious, e.g. in rheumatic fever)

- Symptoms in young children tend to be more nonspecific, with generalized malaise, poor appetite, abdominal pain, and chronic cough. Later stages of the illness will present with respiratory symptoms with increased work of breathing, and is often mistaken for asthma.

Since myocarditis is often due to a viral illness, many patients give a history of symptoms consistent with a recent viral infection, including fever, rash, diarrhea, joint pains, and easily becoming tired.

Myocarditis is often associated with pericarditis, and many people with myocarditis present with signs and symptoms that suggest myocarditis and pericarditis at the same time.

Myocarditis, also known as inflammatory cardiomyopathy, is inflammation of the heart muscle. Symptoms can include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. The duration of problems can vary from hours to months. Complications may include heart failure due to dilated cardiomyopathy or cardiac arrest.

Myocarditis is most often due to a viral infection. Other causes include bacterial infections, certain medications, toxins, and autoimmune disorders. A diagnosis may be supported by an electrocardiogram (ECG), increased troponin, heart MRI, and occasionally a heart biopsy. An ultrasound of the heart is important to rule out other potential causes such as heart valve problems.

Treatment depends on both the severity and the cause. Medications such as ACE inhibitors, beta blockers, and diuretics are often used. A period of no exercise is typically recommended during recovery. Corticosteroids or intravenous immunoglobulin (IVIG) may be useful in certain cases. In severe cases an implantable cardiac defibrillator or heart transplant may be recommended.

In 2013, about 1.5 million cases of acute myocarditis occurred. While people of all ages are affected, the young are most often affected. It is slightly more common in males than females. Most cases are mild. In 2015 cardiomyopathy, including myocarditis, resulted in 354,000 deaths up from 294,000 in 1990. The initial descriptions of the condition are from the mid-1800s.

Carditis is the inflammation of the heart or its surroundings. The plural of carditis is carditides.

It is usually studied and treated by specifying it as:

- Pericarditis is the inflammation of the pericardium

- Myocarditis is the inflammation of the heart muscle

- Endocarditis is the inflammation of the endocardium

- Pancarditis is the inflammation of the entire heart: the epicardium, the myocardium and the endocardium

- Reflux carditis refers to a possible outcome of esophageal reflux (also known as GERD), and involves inflammation of the esophagus/stomach mucosa

These depend on the amount of inflammation. These are covered in their relevant articles.

- Acute: Heart failure; pericardial effusion; etc.

- Chronic: Valve diseases as noted above; Reduced cardiac output; Exercise intolerance.

These are the typical mechanisms of autoimmunity. Autoantibodies or auto-toxic T-lymphocyte mediated tissue destruction. The process is aided by neutrophils, the complement system, tumor necrosis factor alpha, etc.

Aetiologically, these are most commonly seen in children with a history of sore throat caused by a streptococcal infection. This is similar to the post-streptococcal glomerulonephritis. Here, the anti-bacterial antibodies cross react with the heart antigens causing inflammation.

Inflammatory damage leads to the following:

- Pericarditis: Here the pericardium gets inflamed. Acutely, it can cause pericardial effusion leading to cardiac tamponade and death. After healing, there may be fibrosis and adhesion of the pericardium with the heart leading to constriction of the heart and reduced cardiac function.

- Myocarditis: Here the muscle bulk of the heart gets inflamed. Inflamed muscles have reduced functional capacity. This may be fatal, if left untreated as is in a case of pancarditis. On healing, there will be fibrosis and reduced functional capacity.

- Endocarditis: Here the inner lining of the heart is inflamed, including the heart valves. This may cause a valve prolapse, adhesion of the adjacent cusps of these valves and occlusion of the flow tracts of blood through the heart causing diseases called valve stenosis.

Symptoms in eosinophilc myocarditis are highly variable. They tend to reflect the many underlying disorders causing eosinophil dysfunction as well as the widely differing progression rates of cardiac damage. Before cardiac symptoms are detected, some 66% of cases have symptoms of a common cold and 33% have symptoms of asthma, rhinitis, urticarial, or other allergic disorder. Cardiac manifestations of eosinophilic myocarditis range from none to life-threatening conditions such as cardiogenic shock or sudden death due to abnormal heart rhythms. More commonly the presenting cardiac symptoms of the disorder are the same as those seen in other forms of heart disease: chest pain, shortness of breath, fatigue, chest palpitations, light headedness, and syncope. In its most extreme form, however, eosinophilic myocarditis can present as acute necrotizing eosinophilic myocarditis, i.e. with symptoms of chaotic and potentially lethal heart failure and heart arrhythmias. This rarest form of the disorder reflects a rapidly progressive and extensive eosinophilic infiltration of the heart that is accompanied by massive myocardial cell necrosis.

Hypereosinophilia (i.e. blood eosinophil counts at or above 1,500 per microliter) or, less commonly, eosinophilia (counts above 500 but below 1,500 per microliter) are found in the vast majority of cases of eosinophilic myocarditis and are valuable clues that point to this rather than other types of myocarditis or myocardial injuries. However, elevated blood eosinophil counts may not occur during the early phase of the disorder. Other, less specific laboratory findings implicate a cardiac disorder but not necessarily eosinophilic myocarditis. These include elevations in blood markers for systemic inflammation (e.g. C reactive protein, erythrocyte sedimentation rate), elevations in blood markers for cardiac injury (e.g. creatine kinase, troponins); and abnormal electrocardiograms ( mostly ST segment-T wave abnormalities).

Myopericarditis is a combination of both myocarditis and pericarditis appearing in a single individual, namely inflammation of both the pericardium and the heart muscle. It can involve the presence of fluid in the heart. Myopericarditis refers primarily to a pericarditis with lesser myocarditis, as opposed to a perimyocarditis, though the two terms are often used interchangeably. Both will be reflected on an ECG. Myo-pericarditis usually involves inflammation of the pericardium, or the sac covering the heart.

The ACAM2000 smallpox vaccine has been known to cause myopericarditis in some people.

Eosinophilic coronary periarteritis is a heart disorder caused by extensive eosinophilic infiltration of the adventitia and periadventitia, i.e. the soft tissues, surrounding the coronary arteries. The intima, tunica media, and tunica intima layers of these arteries remain intact and are generally unaffected. Thus, this disorder is characterized by episodes of angina, particularly Prinzmetal's angina, and sudden death due to heart dysfunction. The disorder is considered distinct from eosinophilic myocarditis.

Idiopathic giant-cell myocarditis (IGCM) is a cardiovascular disease of the muscle of the heart (myocardium).

The condition is rare; however, it is often fatal and there is no proven cure because of the unknown nature of the disorder.

IGCM frequently leads to death with a high rate of about 70% in first year. A patient with IGCM typically presents with symptoms of heart failure, although some may present initially with ventricular arrhythmia or heart block. Median age from the time the disease is diagnosed to the time of death is approximately 6 months. 90% of patients are either deceased by the end of 1 year or have received a heart transplant. Diagnosis is made by endomyocardial biopsy during heart catheterization. Biopsy shows multinucleated giant cells and thus the name. While previously cases universally required heart transplantation, recent studies show that two thirds of patients can survive past one year with high doses of immunosuppressants such as prednisone and cyclosporine. The transplanted heart has a high chance of disease recurrence. Compared to lymphocytic (presumed viral) myocarditis, giant cell myocarditis is much more severe with much more rapid progression.

It is suggested to be caused by T-lymphocytes.

Non-specific interstitial pneumonia (NSIP) is a form of idiopathic interstitial pneumonia.

Most common:

- Chest Pain

- Cough

- Fever

- Shortness of breath

- Joint pain, stiffness, swelling

- Skin nodules

People may not present with all these symptoms or non at all.

It has been suggested that idiopathic nonspecific interstitial pneumonia has an autoimmune mechanism, and is a possible complication of undifferentiated connective tissue disease.

In patients with lymphocytic interstitial pneumonia, these patients may present with lymphadenopathy, enlarged liver, enlarged spleen, enlarged salivary gland, thickening and widening of the extremities of the fingers and toes (clubbing), and breathing symptoms such as shortness of breath and wheezing.

Rheumatoid Lung Disease, also called Rheumatoid Lung is a disease of the lung associated with RA, rheumatoid arthritis. Rheumatoid lung disease is characterized by pleural effusion, pulmonary fibrosis, lung nodules and pulmonary hypertension. Common symptoms associated with the disease include shortness of breath, cough, chest pain and fever. It is estimated that about one quarter of people with rheumatoid arthritis develop this disease, which are more likely to develop among elderly men with a history of smoking.

Rheumatoid lung is separate from but often associated with Interstitial lung disease(ILD).

The typical symptoms of UIP are progressive shortness of breath and cough for a period of months. In some patients, UIP is diagnosed only when a more acute disease supervenes and brings the patient to medical attention.

Possible causes of lymphocytic interstitial pneumonia include the Epstein-Barr virus and Human Immunodeficiency Virus.

Pneumonitis or pulmonitis is an inflammation of lung tissue due to factors other than microorganisms. Those can be radiation therapy of the chest , exposure to medications used during chemo-therapy, the inhalation of debris (ie animal dander), of food particles during vomiting, herbicides or fluorocarbons and some systemic diseases.

It is distinguished from pneumonia on the basis of causation as well as its manifestation since pneumonia can be described as pneumonitis combined with consolidation and exudation of lung tissue due to infection with microorganism.

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.

The cause of the scarring in UIP may be known (less commonly) or unknown (more commonly). Since the medical term for conditions of unknown cause is "idiopathic", the clinical term for UIP of unknown cause is idiopathic pulmonary fibrosis (IPF). Examples of known causes of UIP include systemic sclerosis/scleroderma, rheumatoid arthritis, asbestosis, and prolonged use of medications such as nitrofurantoin or amiodarone.

Desquamative interstitial pneumonia is a form of idiopathic interstitial pneumonia featuring elevated levels of macrophages.

Its name is derived from the former belief that these macrophages were pneumocytes that had desquamated.

It is associated with patients with a history of smoking.

Treatment with methylprednisolone has been reported.

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.

It can be classified into acute interstitial pneumonitis, blood pneumonitis, lymphocytic interstitial pneumonitis, radiation pneumonitis, and uremic pneumonitis.

Dilated cardiomyopathy can be due to pericardial effusion or infective endocarditis, especially in intravenous drug users which are common in the HIV population. However, the most researched cause of cardiomyopathy is myocarditis (myocardial inflammation and infection) caused by HIV-1, which the main subtype of HIV (the other being HIV-2), with greater likelihood of transmission and shorter period between infection and illness. HIV-1 virions infect cardiomyocytes in patches but there is no direct correlation between viral infection and dysfunction of cardiomyocytes.

HIV-related cardiomyopathy is often not associated with any specific opportunistic infection, and approximately 40% of patients have not experienced any opportunistic infection before the onset of cardiac symptoms.

Heart problems are very important in people with Human Immunodeficiency Virus (HIV) as Acquired ImmunoDeficiency Syndrome (AIDS) patients with left ventricular dysfunction have a median survival of 101 days as compared to 472 days in AIDS patients with healthy hearts. HIV is a major cause of cardiomyopathy (problems with the heart muscle that reduce the efficiency with which the heart pumps blood). The most common type of HIV induced cardiomyopathy is dilated cardiomyopathy also known as eccentric ventricular hypertrophy which leads to impaired contraction of the ventricles due to volume overload. The annual incidence of HIV associated dilated cardiomyopathy was 15.9/1000 before the introduction of highly active antiretroviral therapy (HAART). However, in 2014, a study found that 17.6% of HIV patients have dilated cardiomyopathy (176/1000) meaning the incidence has greatly increased.

Acute interstitial pneumonitis (also known as acute interstitial pneumonia or Hamman–Rich syndrome) is a rare, severe lung disease that usually affects otherwise healthy individuals. There is no known cause or cure.

Acute interstitial pneumonitis is often categorized as both an interstitial lung disease and a form of acute respiratory distress syndrome (ARDS) but it is distinguished from the "chronic" forms of interstitial pneumonia such as idiopathic pulmonary fibrosis.