Recurrent Cutaneous Mycobacterium chelonae Infection With an IgM ‐Predominant Antibody Response in DiGeorge Syndrome

A young girl with DiGeorge syndrome developed recurrent cutaneous infection caused by Mycobacterium chelonae infection while receiving immunosuppressive therapy. Immunological evaluation demonstrated reduced T‐cell proportions and impaired humoral immunity. Western blot analysis using recurrence‐phase serum showed IgM reactivity against the recurrent isolate but no detectable IgG reactivity. These findings suggest impaired T‐cell–dependent class‐switch recombination, resulting in an IgM‐predominant humoral response in DiGeorge syndrome.