CASE 9
Mark is 2 years of age and has already suffered from more than his share of childhood infections and prolonged episodes of diarrhea. He has been hospitalized twice for bacterial pneumonia, has had almost constant (according to his mother) viral infections, and twice has had oral thrush (Candida albicans). He is under the care of an infectious disease specialist at a tertiary care center, who now believes he understands the etiology of the problem. Further exploration of the family tree revealed evidence of a distant great-grandparent who was perpetually “sick” and two cousins, Sally and Joe, who have recurrent infectious illnesses. Simple blood tests performed on many occasions have never revealed defects in the total number of B cells and T cells or neutrophils/monocytes. However, T cell subset analysis by flow cytometry indicated severe CD4+ lymphopenia and serum immunoglobulin levels, although present, were low. Antibody titers to childhood immunizations were negligible. Nitroblue tetrazolium tests indicated a normal respiratory burst after phagocytosis (see Case 6).
QUESTIONS FOR GROUP DISCUSSION
RECOMMENDED APPROACH
Implications/Analysis of Clinical History
A defect in phagocytes, leukocyte trafficking, or complement could account for the bacterial infections, but they would not, alone, account for other types of infection. A clinical history of fungal or viral infections strongly suggested a defect in T cell function. Therefore, a defect that affects both B cells and T cells should be considered.
