Rubinstein-Taybi Syndrome with thymic hypoplasia.

We report the autopsy findings in a 20-month-old boy with Rubinstein-Taybi syndrome and DiGeorge sequence. No visible thymus was demonstrated at the time of autopsy. With careful microscopic examination, a few pieces of thymic tissues found near the thyroid gland showed remarkable depletion of both thymocytes and cortical epithelial cells. Immunohistological staining with T-cell surface antigens resulted in a definite positive reaction. Repeated respiratory infections present in this patient may, in part, be attributable to thymic hypoplasia. Other major anomalies included broad thumbs and great toes, microphthalmia, arrhinencephaly, patent ductus arteriosus, stenosis of the ureterovesicular junction, bilateral cryptorchidism, and minor facial anomalies.