Giulia McGettigan was born full term with a malformed jaw, cleft palate, a ventricular septal defect, and hypocalcemia. Within 48 hours of birth she developed muscle tetany, convulsions, tachypnea, and a systolic murmur

Question

A chest X-ray showed an enlarged heart and the absence of a thymic shadow. Blood tests showed severely depleted levels of CD4 and CD8 T cells; B-cell numbers were low but within normal range. Parathyroid hormone was undetectable. Fluorescence in situ hybridization of the buccal mucosa revealed a small deletion in the long arm of chromosome 22. Giulia failed to thrive and battled chronic diarrhea and opportunistic infections, including oral candidiasis and Pneumocystis jirovecii, the latter infection causing her death. Giulia most probably had which of the following immunodeficiency diseases?
a. AIDS
b. DiGeorge syndrome
c. bare lymphocyte syndrome
d. chronic granulomatous disease
e. hyper IgM syndrome.

Answer 1

Rationale: The correct answer is b. Depletion of T cells, but not of B cells, and the absence of a thymic shadow on the X-ray are critical clues. Development of both CD8 and CD4 T cells is affected in this patient because the thymus is the primary lymphoid organ required for T-cell development. Bare lymphocyte syndrome affects either CD8 (type I) or CD4 (type II), but not both. Although patients without a thymus succumb to infections also common in individuals with AIDS, this option can be ruled out because Giulia lacks CD8 T cells, a condition not seen in AIDS patients. Chronic granulomatous disease is a defect of neutrophil, not T-cell, function.