A 21-year-old woman has a history since childhood of recurrent episodes of swelling of the submucosal and subcutaneous tissue of the gastrointestinal and respiratory tracts. Her C1 inhibitor level is less than 5% of the reference value. These findings support a diagnosis of:

Ans. (b)Hereditary angioedema is caused by deficient levels of C1 inhibitor. DiGeorge syndrome is caused by aberrant development of the thymus. Nutrition based immunodeficiencies are not characteristically identified by severely reduces levels of specific cell types or related molecules. Paroxysmal nocturnal hemoglobinuria is caused by the deficiency of CD59.