CASE 2
RD is a 1-year-old adopted boy in your practice who has had a surprisingly high (eight) number of severe recurrent viral and fungal infections (e.g., respiratory syncytial virus, Candida albicans) during his first 14 months. Each of these has eventually resolved, albeit very slowly, and the fungal infections have responded to the appropriate medication. You are nevertheless concerned to find the underlying cause of his problem. Recent chest radiographs performed at a local hospital to rule out pneumonia have been returned to you by the radiologist with a note that there was an abnormality, in particular an apparent absence of a thymic shadow. The radiologist has asked if there are any other stigmata of congenital absence of a thymus. As you describe this child’s history, you also mention his physical appearance (eyes widely separated, low ears, cleft palate).
QUESTIONS FOR GROUP DISCUSSION
RECOMMENDED APPROACH
Implications/Analysis of Family History
A family history is not possible because the child has been adopted.
Implications/Analysis of Clinical History
Viral and fungal infections point us immediately to a defect in T cells (Fig. 2-1). Although a defect in phagocytes may result in increased susceptibility to fungal infections, T cells are the key players in both viral and fungal infections. (Recall that the patient in Case 1 had a clinical history of fungal, viral, and bacterial infections.)
Implications/Analysis of Laboratory Investigation
The absence of a thymic shadow indicates a defect during embryogenesis resulting in partial or complete absence of a thymus. When the defect is very severe, T cell maturation cannot occur in the thymus. A deficiency of T cells would explain RD’s clinical history. Additionally, RD’s physical appearance is consistent with that of children diagnosed with this defect.
