Lymphomatoid granulomatosis (LYG or LG) is a very rare lymphoproliferative disorder first characterized in 1972. Lymphomatoid means lymphoma-like and  granulomatosis denotes the microscopic characteristic of the presence of granulomas with polymorphic lymphoid infiltrates and focal necrosis within it. LG most commonly affects middle aged people, but has occasionally been observed in young people. Males are found to be affected twice as often as females. Causes
Lymphomatoid granulomatosis involves malignant B cells and reactive, non-malignant T cells and is almost always associated with infection of the malignant B cells by the Epstein-Barr virus; it is therefore considered to be a form of the Epstein-Barr virus-associated lymphoproliferative diseases. The disease is believed to be induced by a combination of Epstein Barr virus infection and immunosuppression through immunosuppressive drugs (with case reports of methotrexate and azathioprine), infections such as HIV or chronic viral hepatitis or endogenous T cell defects. Pathophysiology
The onset of the disease results in proliferation of EBV-infected malignant B-cells and a cytotoxic T-cell response which in turn leads to organ infiltration and dysfunction of the affected organs. The disease typically always relapse after successful treatment due to inability of the immune system and current viral drugs to eliminate an EBV-infection. If the onset of the disease can be linked to use of immunosuppressive drugs then discontinuation of these drugs may hinder a relapse. Organs usually affected are the skin, lungs, central nervous system while liver and kidney are affected to lesser extent.
Risk factors include valvular heart disease including rheumatic disease, congenital heart disease, artificial valves, hemodialysis, intravenous drug use, and electronic pacemakers. The bacterial most commonly involved are streptococci or staphylococci.The diagnosis of infective endocarditis relies on the Duke criteria, which were originally described in 1994 and modified in 2000. Clinical features and microbiological examinations are the first steps to diagnose an infective endocarditis. The imaging is also crucial. Echocardiography is the cornerstone of imaging modality in the diagnosis of infective endocarditis. Alternative imaging modalities as computer tomography, magnetic resonance imaging, and positron emission tomography/computer tomography (PET/CT) with 2-[18F]fluorodeoxyglucose (FDG) are playing an increasing role in the diagnosis and management of infective endocarditis.The usefulness of antibiotics following dental procedures for prevention is unclear. Some recommend them in those at high risk. Treatment is generally with intravenous antibiotics. The choice of antibiotics is based on the blood cultures. Occasionally heart surgery is required.The number of people affected is about 5 per 100,000 per year. Rates, however, vary between regions of the world. Males are affected more often than females. The risk of death among those infected is about 25%. Without treatment it is almost universally fatal. Non-infective 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.