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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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Common variable deficiency is due to -
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The correct answer is  Most patients with common variable immunodeficiency have normal or near-normal numbers of B cells in the blood and lymphoid tissues.
These B cells, however, are not able to differentiate into plasma cells.
The clinical manifestations are caused by antibody deficiency.
The feature common to all patients is hypogammaglobulinemia, generally affecting all the antibody classes but sometimes only IgG.