Pneumonia and other conditions caused by common variable immunodeficiency

Among immunodeficiencies there is one called common variable immunodeficiency（CVI）; when it is lacking, respiratory tract infections and chronic diseases of the digestive tract readily occur, and a small number of people also have enlarged lymph nodes. Across these three major categories, the various diseases grouped together can number in the dozens, or even in the hundreds. Among respiratory tract infections, bacterial acute and chronic sinusitis very easily appears, along with otitis media, pharyngitis, tracheitis, pneumonia, and so on, and it can lead to bronchiectasis.

When the body lacks the common variable immune gene, it loses the ability to resist pathogens such as Haemophilus influenzae, Staphylococcus, Streptococcus and pneumococcus, and organisms such as Mycoplasma, Pneumocystis carinii, varicella-zoster virus, Candida and herpes simplex virus, so infection and the above diseases readily occur. Because people who lack the common variable immune gene have a weaker autoantibody response, they become infected and develop severe respiratory tract diseases.

In a small number of people who lack the common variable immune gene, after respiratory tract inflammation appears, nervous system diseases also readily develop; common complications include chronic purulent meningitis and viral encephalitis. Another feature is that the condition is chronic and treatment is long and drawn out. As a result, some cases cause organic damage to the affected tissues, with the onset of bone cancer, thymoma, lymphoma and various thyroid diseases, and some also form non-caseating granulomas, which in turn involve the lungs, liver, spleen and skin.

Digestive tract diseases such as chronic malabsorption syndrome, steatorrhea, folate and vitamin B12 deficiency, lactose intolerance, disaccharidase deficiency, and protein-losing enteropathy are also diseases that people lacking the common variable immune gene are prone to. Intestinal symptoms caused by Giardia lamblia, and nodular lymphoid hyperplasia, can also appear. Moreover, a small number of people lacking the common variable immune gene can develop enlarged lymph nodes and splenomegaly, and when the cause is unknown, it is easily misdiagnosed as lymphoma.