Among the signs of subacute bacterial endocarditis are:

- Malaise

- Weakness

- Excessive sweat

- Fever

Subacute bacterial endocarditis (also called endocarditis lenta) is a type of endocarditis (more specifically, infective endocarditis). Subacute bacterial endocarditis can be considered a form of type III hypersensitivity.

Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or the surfaces of intracardiac devices. Endocarditis is characterized by lesions, known as "vegetations", which is a mass of platelets, fibrin, microcolonies of microorganisms, and scant inflammatory cells. In the subacute form of infective endocarditis, the vegetation may also include a center of granulomatous tissue, which may fibrose or calcify.

There are several ways to classify endocarditis. The simplest classification is based on cause: either "infective" or "non-infective", depending on whether a microorganism is the source of the inflammation or not. Regardless, the diagnosis of endocarditis is based on clinical features, investigations such as an echocardiogram, and blood cultures demonstrating the presence of endocarditis-causing microorganisms. Signs and symptoms include fever, chills, sweating, malaise, weakness, anorexia, weight loss, splenomegaly, flu-like feeling, cardiac murmur, heart failure, petechia of anterior trunk, Janeway's lesions, etc.

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.

Endocarditis can also be classified by the side of the heart affected:

- Patients who inject opioids such as heroin, or other drugs such as methamphetamine intravenously, may introduce infection which can travel to the right side of the heart classically affecting the tricuspid valve, and most often caused by "S. aureus".

- Regardless of cause, left-sided endocarditis is more common in both IV drug users and non-drug users than right-sided endocarditis.

Nonbacterial thrombotic endocarditis (NBTE) is most commonly found on previously undamaged valves. As opposed to infective endocarditis, the vegetations in NBTE are small, sterile, and tend to aggregate along the edges of the valve or the cusps. Also unlike infective endocarditis, NBTE does not cause an inflammation response from the body. NBTE usually occurs during a hypercoagulable state such as system-wide bacterial infection, or pregnancy, though it is also sometimes seen in patients with venous catheters. NBTE may also occur in patients with cancers, particularly mucinous adenocarcinoma where Trousseau syndrome can be encountered. Typically NBTE does not cause many problems on its own, but parts of the vegetations may break off and embolize to the heart or brain, or they may serve as a focus where bacteria can lodge, thus causing infective endocarditis.

Another form of sterile endocarditis is termed Libman–Sacks endocarditis; this form occurs more often in patients with lupus erythematosus and is thought to be due to the deposition of immune complexes. Like NBTE, Libman-Sacks endocarditis involves small vegetations, while infective endocarditis is composed of large vegetations. These immune complexes precipitate an inflammation reaction, which helps to differentiate it from NBTE. Also unlike NBTE, Libman-Sacks endocarditis does not seem to have a preferred location of deposition and may form on the undersurfaces of the valves or even on the endocardium.

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.

Grossly, vegetations form along lines of valve closure and are generally symmetric with a smooth or verrucoid (warty) texture. Histologically, lesions are composed of fibrin (eosinophilic) and platelets but, unlike bacterial etiologies, contain little evidence of PMNs, microorganisms or inflammation.

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

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

The disease affects the valves with the following predilection: mitral valve > aortic valve > tricuspid valve > pulmonary valve

Cat-scratch disease commonly presents as tender, swollen lymph nodes near the site of the inoculating bite or scratch or on the neck, and is usually limited to one side. This condition is referred to as regional lymphadenopathy and occurs 1–3 weeks after inoculation. Lymphadenopathy in CSD most commonly occurs in the arms, neck, or jaw, but may also occur near the groin or around the ear. A vesicle or an erythematous papule may form at the site of initial infection. Most patients also develop systemic symptoms such as malaise, decreased appetite, and aches. Other associated complaints include headache, chills, muscular pains, joint pains, arthritis, backache, and abdominal pain. It may take 7 to 14 days, or as long as two months, for symptoms to appear. Most cases are benign and self-limiting, but lymphadenopathy may persist for several months after other symptoms disappear. The disease usually resolves spontaneously, with or without treatment, in one month.

In rare situations, CSD can lead to the development of serious neurologic or cardiac sequelae such as meningoencephalitis, encephalopathy, seizures, or endocarditis. Endocarditis associated with "Bartonella" infection has a particularly high mortality. Parinaud's oculoglandular syndrome is the most common ocular manifestation of CSD, and is a granulomatous conjunctivitis with concurrent swelling of the lymph node near the ear. Optic neuritis or neuroretinitis is one of the atypical presentations.

Immunocompromised patients are susceptible to other conditions associated with "B. henselae" and "B. quintana", such as bacillary angiomatosis or bacillary peliosis. Bacillary angiomatosis is primarily a vascular skin lesion that may extend to bone or be present in other areas of the body. In the typical scenario, the patient has HIV or another cause of severe immune dysfunction. Bacillary peliosis is caused by "B. henselae" that most often affects patients with HIV and other conditions causing severe immune compromise. The liver and spleen are primarily affected, with findings of blood-filled cystic spaces on pathology. In 2015 a Toledo, Ohio woman lost eyesight in an eye after a cat licked it.

An infected aneurysm (also known as mycotic aneurysm or microbial arteritis) is an aneurysm arising from bacterial infection of the arterial wall. It can be a common complication of the hematogenous spread of bacterial infection.

William Osler first used the term "mycotic aneurysm" in 1885 to describe a mushroom-shaped aneurysm in a patient with subacute bacterial endocarditis. This may create considerable confusion, since "mycotic" is typically used to define fungal infections. However, mycotic aneurysm is still used for all extracardiac or intracardiac aneurysms caused by infections, except for syphilitic aortitis.

The term "infected aneurysm," proposed by Jarrett and associates is more appropriate, since few infections involve fungi. According to some authors, a more accurate term might have been endovascular infection or infective vasculitis, because mycotic aneurysms are not due to a fungal organism.

Mycotic aneurysms account for 2.6% of aortic aneurysms. For the clinician, early diagnosis is the cornerstone of effective treatment. Without medical or surgical management, catastrophic hemorrhage or uncontrolled sepsis may occur. However, symptomatology is frequently nonspecific during the early stages, so a high index of suspicion is required to make the diagnosis.

Intracranial mycotic aneurysms (ICMAs) complicate about 2% to 3% of infective endocarditis (IE) cases, although as many as 15% to 29% of patients with IE have neurologic symptoms.

The secondary stages of syphilis persists to be more dangerous to the systems of the human body. The disseminated disease can cause constitutional symptoms and condylomata lata. Many treponemes are present in chancres in the primary stage; however, condylomata lata is usually present in the secondary stage. The pathogen can spread through blood, which can infect the vessels in the body. The infection of the heart, muscles, and vessels in the body can lead to meningovascular syphilis. Generally, rashes may start developing on the hands and soles of the feet, and it can spread to various parts of skin on the body. Other symptoms may include sore throat, headache, joint pain, fever, and patches of hair loss. As in stage one, lesions may start to form on the body, but in this stage in particular, lesions are found in mucous membranes of the mouth, throat, bones, and internal organs. Also common with stage one, the symptoms and signs of secondary syphilis will go away with or without treatment and medication. The diagnosis includes serology nonspecific and specific, both positive. The secondary stage is however highly infectious because the bacteria is spreading drastically throughout the body.

Patients can develop two clinical phases: an acute septic phase and a chronic eruptive phase associated with skin lesions. In the acute phase (also known as Oroya fever or "fiebre de la Oroya"), "B. bacilliformis" infection is a sudden, potentially life-threatening infection associated with high fever and decreased levels of circulating red blood cells (i.e., hemolytic anemia)and transient immunosuppression. "B. bacilliformis" is considered the most deadly species to date, with a death rate of up to 90% during the acute phase, which typically lasts two to four weeks. Peripheral blood smears show anisomacrocytosis with many bacilli adherent to red blood cells. Thrombocytopenia is also seen and can be very severe. Neurologic manifestations (neurobartonellosis) are altered mental status, agitation, or even coma, ataxia, spinal meningitis, or paralysis. It is seen in 20% of patients with acute infection, in which the prognosis is very guarded with an about 50% mortality. The most feared complication is overwhelming infection mainly by Enterobacteriaceae, particularly "Salmonella" (both "S. typhi" and " S. "non-"typhi", as well as reactivation of toxoplasmosis and other opportunistic infections .

The chronic manifestation consists of a benign skin eruption with raised, reddish-purple nodules (angiomatous tumours). The bacterium can be seen microscopically, if a skin biopsy is silver stained (the Warthin–Starry method).

"B. henselae" is the etiologic agent for peliosis hepatis, which is defined as a vascular proliferation of sinusoid hepatic capillaries resulting in blood-filled spaces in the liver in HIV patients and organ transplant recipients. Peliosis hepatis can be associated with peliosis of the spleen, as well as bacillary angiomatosis of the skin in HIV patients.

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.

Syphilitic aortitis (SA) is inflammation of the aorta associated with the tertiary stage of syphilis infection. SA begins as inflammation of the outermost layer of the blood vessel, including the blood vessels that supply the aorta itself with blood, the vasa vasorum. As SA worsens, the vasa vasorum undergo hyperplastic thickening of their walls thereby restricting blood flow and causing ischemia of the outer two-thirds of the aortic wall. Starved for oxygen and nutrients, elastic fibers become patchy and smooth muscle cells die. If the disease progresses, syphilitic aortitis leads to an aortic aneurysm. Unlike atherosclerosis, which typically manifests in older people, syphilitic aortitis typically affects those under the age of 50. It has become rare in the developed world with the advent of penicillin treatments after World War II.

Autoimmune heart diseases are the effects of the body's own immune defense system mistaking cardiac antigens as foreign and attacking them leading to inflammation of the heart as a whole, or in parts. The commonest form of autoimmune heart disease is rheumatic heart disease or rheumatic fever.

The several forms of the infection are:

- Skin/subcutaneous tissue disease is a septic phlegmon that develops classically in the hand and forearm after a cat bite. Inflammatory signs are very rapid to develop; in 1 or 2 hours, edema, severe pain, and serosanguineous exudate appear. Fever, moderate or very high, can be seen, along with vomiting, headache, and diarrhea. Lymphangitis is common. Complications are possible, in the form of septic arthritis, osteitis, or evolution to chronicity.

- Sepsis is very rare, but can be as fulminant as septicaemic plague, with high fever, rigors, and vomiting, followed by shock and coagulopathy.

- Pneumonia disease is also rare and appears in patients with some chronic pulmonary pathology. It usually presents as bilateral consolidating pneumonia, sometimes very severe.

- Zoonosis, pasteurellosis can be transmitted to humans through cats.

Other locations are possible, such as septic arthritis, meningitis, and acute endocarditis, but are very rare.

Tertiary syphilis may occur approximately 3 to 15 years after the initial infection, and may be divided into three different forms: gummatous syphilis (15%), late neurosyphilis (6.5%), and cardiovascular syphilis (10%). Without treatment, a third of infected people develop tertiary disease. People with tertiary syphilis are not infectious.

Gummatous syphilis or late benign syphilis usually occurs 1 to 46 years after the initial infection, with an average of 15 years. This stage is characterized by the formation of chronic gummas, which are soft, tumor-like balls of inflammation which may vary considerably in size. They typically affect the skin, bone, and liver, but can occur anywhere.

Neurosyphilis refers to an infection involving the central nervous system. It may occur early, being either asymptomatic or in the form of syphilitic meningitis, or late as meningovascular syphilis, general paresis, or tabes dorsalis, which is associated with poor balance and lightning pains in the lower extremities. Late neurosyphilis typically occurs 4 to 25 years after the initial infection. Meningovascular syphilis typically presents with apathy and seizure, and general paresis with dementia and tabes dorsalis. Also, there may be Argyll Robertson pupils, which are bilateral small pupils that constrict when the person focuses on near objects but do not constrict when exposed to bright light.

Cardiovascular syphilis usually occurs 10–30 years after the initial infection. The most common complication is syphilitic aortitis, which may result in aneurysm formation.

Death from congenital syphilis is usually due to bleeding into the lungs.

Granuloma inguinale (also known as donovanosis) is a bacterial disease caused by "Klebsiella granulomatis" (formerly known as "Calymmatobacterium granulomatis") characterized by ulcerative genital lesions. It is endemic in many less developed regions. It is also known as donovanosis, granuloma genitoinguinale, granuloma inguinale tropicum, granuloma venereum, granuloma venereum genitoinguinale, lupoid form of groin ulceration, serpiginous ulceration of the groin, ulcerating granuloma of the pudendum, and ulcerating sclerosing granuloma.

The disease often goes untreated because of the scarcity of medical treatment in the countries in which it is found. In addition, the painless genital ulcers can be mistaken for syphilis. The ulcers ultimately progress to destruction of internal and external tissue, with extensive leakage of mucus and blood from the highly vascular lesions. The destructive nature of donovanosis also increases the risk of superinfection by other pathogenic microbes.

Inflammatory involvement of tertiary syphilis begins at the adventitia of the aortic arch which progressively causes obliterative endarteritis of the vasa vasorum. This leads to narrowing of the lumen of the vasa vasorum, causing ischemic injury of the medial aortic arch and then finally loss of elastic support and dilation of the vessel. Dissection of the aortic arch is rare due to medial scarring. As a result of this advanced disease process, standard methods of angiography/angioplasty may be impossible for those with suspected coronary heart disease. However, these patients may be candidates for diagnostic CT as a less invasive modality. This disorder is also known eponymously as Heller-Döhle syndrome.