THYMIC HYPOPLASIA AND T-CELL DEFICIENCY IN ECTODERMAL DYSPLASIA - CASE-REPORT AND REVIEW OF THE LITERATURE

Ectodermal dysplasia is a heterogeneous disorder that includes a const ellation of congenital malformations occasionally associated with mild to moderate immune dysfunction. In this report, we describe a female infant with ectodermal dysplasia who was found to have thymic hypoplas ia but no other phenotypic features of the DiGeorge anomalad. She expe rienced Candida parapsilosis sepsis at 1 week of age and a skin infect ion with Mycobacterium chelonii at 6 months. The numbers of blood B ce lls were normal and serum immunoglobulins normal to slightly reduced, but serum antibody responses of all immunoglobulin isotypes to protein immunogens were absent. Blood T cells were profoundly reduced and pro liferative responses of T cells to mitogens were blunted. In contrast, there was an increased number of natural killer (NK) cells and increa sed NK activity in the blood. Over the first year of life, some of the immunodeficiencies resolved. Although the numbers of blood T cells (1 7% of total lymphocytes) remained low, proliferative responses to mito gens normalized and specific antibody responses improved. It seems lik ely that the thymic hypoplasia in this case was due to a paucity of ec todermal elements in the developing thymus, and that the immune defect s were largely secondary to that event. In that respect, this human mo del of ectodermal dysplasia and thymic hypoplasia resembled the ectode rmal/thymic defects found in the nude mouse. (C) 1994 Academic Press, Inc.