A mother brought her daughter with complaints of diarrhea. Lab investigations revealed Giardia lamblia. She had the same complaint before few weeks and was treated. She also had history of getting recurrent chest infections. This girl may have:

Common variable immunodeficiency (CVID) is a disorder characterized by poor production of immunoglobulins in response to antigenic stimuli. This limited humoral response to antigens leads to recurrent sinus and pulmonary infections, often caused by Streptococcus pneumoniae and other bacterial pathogens. Recurrent pulmonary infections over time may lead to bronchiectasis, a common complication of CVID in adults. Patients with CVID may also have chronic enteric infection with Giardia lamblia and chronic meningoencephalitis due to enterovirus. Ref: Hammond S.P., Baden L.R. (2012). Chapter 198. Infections of the Immunocompromised Host. In G.V. Lawry, S.C. McKean, J. Matloff, J.J. Ross, D.D. Dressler, D.J. Brotman, J.S. Ginsberg (Eds), Principles and Practice of Hospital Medicine.