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Common variable immunodeficiency (CVID) is the most commonly diagnosed primary immunodeficiency. It is characterized by low antibody levels and recurrent infections. == Signs and symptoms == CVID is a clinically heterogeneous disease. Its main features are hypogammaglobulinemia and recurrent infections. Hypogammaglobulinemia manifests as a significant decrease in the levels of IgG antibodies, usually alongside IgA antibodies; IgM antibody levels are also decreased in about 50% of patients. Infections are a direct result of the low antibody levels in the circulation of patients, which do not adequately protect them against pathogens. The microorganisms that most frequently cause infections in CVID are bacteria Haemophilus influenzae, Streptococcus pneumoniae and Staphylococcus aureus. Pathogens less often isolated from patients include Neisseria meningitidis, Pseudomonas aeruginosa and Giardia lamblia. Infections mostly affect the respiratory tract (nose, sinuses, bronchi, lungs) and the ears; they can also occur at other sites, such as the eyes, skin and gastrointestinal tract. These infections respond to antibiotics but can recur upon their discontinuation. Bronchiectasis can develop when severe, recurrent pulmonary infections are left untreated. In addition to infections, CVID patients can develop complications of different kinds. These include: * autoimmune manifestations, e.g. pernicious anemia, autoimmune haemolytic anemia (AHA), idiopathic thrombocytopenic purpura (ITP), psoriasis, vitiligo, rheumatoid arthritis, primary hypothyroidism, atrophic gastritis. Autoimmunity is the main type of complication in CVID patients, appearing in some form in up to 50% of individuals; * malignancies, particularly Non-Hodgkin's lymphoma and gastric carcinoma; * enteropathy, which manifests with a blunting of intestinal villi and inflammation, and is usually accompanied by symptoms such as abdominal cramps, diarrhea, constipation and, in some cases, malabsorption and weight loss. Symptoms of CVID enteropathy are similar to those of celiac disease, but don't respond to a gluten-free diet. Infectious causes must be excluded before a diagnosis of enteropathy can be made, as CVID patients are more susceptible to intestinal infections, e.g. by Giardia lamblia; * lymphocytic infiltration of tissues, which can cause enlargement of lymph nodes (lymphadenopathy), of the spleen (splenomegaly) and of the liver (hepatomegaly), as well as the formation of granulomas. Anxiety and depression can occur, as a result of dealing with the other symptoms.〔Sanger, David E. ("An Investigation of Coping and Psychosocial Functioning in Persons with Common Variable Immunodeficiency (CVID)" ), ''Barts and The London NHS Trust'', 2003, accessed August 7, 2011.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Common variable immunodeficiency」の詳細全文を読む スポンサード リンク
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