Common variable immunodeficiency is a group of 20-30 primary immunodeficiencies which have a common set of symptoms but with different underlying causes. CVID is believed to be a genetically determined primary immune defect; however, the underlying causes are different. The result of these defects is that the patient doesn't produce sufficient antibodies in response to exposure to pathogens. As a result, the patient's immune system fails to protect them against...
CVID is prevalent in approximately 1 case per 50,000 population in the US and fortunately I'm not one. Here's some info for you: http://www.emedicine.com/derm/topic870.htm
Hope you're feeling better.