Epstein–Barr virus-associated lymphoproliferative diseases
Epstein–Barr virus-associated lymphoproliferative diseases are a group of benign, premalignant, and malignant diseases of lymphoid cells, i.e. B cells, T cells, NK cells, and histiocytic-dendritic cells in which one or more of these cell types is infected with the Epstein–Barr virus (EBV). The virus may be responsible for the development and/or progression of these diseases. In addition to EBV-positive Hodgkin lymphomas, the World Health Organization (2016) includes the following lymphomas, when associated with EBV infection, in this group of diseases: Burkitt lymphoma; large B cell lymphoma, not otherwise specified; diffuse large B cell lymphoma associated with chronic inflammation; fibrin-associated diffuse large B cell lymphoma; primary effusion lymphoma; plasmablastic lymphoma; extranodal NK/T cell lymphoma, nasal type; peripheral T cell lymphoma, not otherwise specified; angioimmunoblastic T cell lymphoma; follicular T cell lymphoma; and systemic T cell lymphoma of childhood. WHO classification
The WHO classification, published in 2001 and updated in 2008, is based upon the foundations laid within the "revised European–American lymphoma classification" (REAL). This system groups lymphomas by cell type (i.e. the normal cell type that most resembles the tumor) and defining phenotypic, molecular, or cytogenetic characteristics. The five groups are shown in the table. Hodgkin lymphoma is considered separately within the WHO and preceding classifications, although it is recognized as being a tumor, albeit markedly abnormal, of lymphocytes of mature B cell lineage.Of the many forms of lymphoma, some are categorized as indolent (e.g. small lymphocytic lymphoma), compatible with a long life even without treatment, whereas other forms are aggressive (e.g.
Chiari 1.5 is a term used when both brainstem and tonsillar herniation through the foramen magnum are present.The diagnosis of a Chiari II malformation can be made prenatally, through ultrasound. Classification
In the late 19th century, Austrian pathologist Hans Chiari described seemingly related anomalies of the hindbrain, the so-called Chiari malformations I, II and III. Later, other investigators added a fourth (Chiari IV) malformation. The scale of severity is rated I – IV, with IV being the most severe. Types III and IV are very rare. Since Dr. Chiaris original descriptions Chiari 0, 1.5, 3.5, and 5 have been described in the medical literature. Types of Chiari malformation
Other conditions sometimes causally associated with Chiari malformation include hydrocephalus, syringomyelia, spinal curvature, tethered spinal cord syndrome, and connective tissue disorders such as Ehlers-Danlos syndrome and Marfan syndrome. Chiari malformation is the most frequently used term for this set of conditions. The use of the term "Arnold–Chiari malformation" has fallen somewhat out of favor over time, although it is used to refer to the type II malformation. Current sources use "Chiari malformation" to describe its four specific types, reserving the term "Arnold-Chiari" for type II only. Some sources still use "Arnold-Chiari" for all four types.Chiari malformation or Arnold–Chiari malformation should not be confused with Budd-Chiari syndrome, a hepatic condition also named for Hans Chiari. In Pseudo-Chiari Malformation, leaking of CSF may cause displacement of the cerebellar tonsils and similar symptoms sufficient to be mistaken for a Chiari I malformation.