This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Medicine
Recurrent Giardiasis is associated with: 
Select and explain. 
A. Severe combined immunodeficiency, B. Common variable immunodeficiency, C. Digeorge syndrome, D. C8 deficiency
B: Common variable immunodeficiency
Answer: B: Common variable immunodeficiency 
Explanation: Common variable immunodeficiency is associated with the deficient production of antibodiesThey have a normal number of B lymphocytes but fail to mature into plasma cellsResults in hypogammaglobulinemia, with a reduction in all classes of Ig but sometimes only IgG is reducedVarious disorders associated:Intestinal disorders:Chronic giardiasisIntestinal malabsorptionAtrophic gastritis(with pernicious anaemia)Chronic pulmonary infections:bronchiectasisOthers:can also present with signs and symptoms of lymphoid malignanciesfeverweight lossanaemiasplenomegalylymphadenopathy(ref: Harrison's 18/e p1849, 2059)