Two-year-old boy with Proteus syndrome and fatal pulmonary thromboembolism.

A 2-year-old boy with a relatively mild form of Proteus syndrome (PS) died suddenly during a previously uncomplicated postsurgical convalescence. Autopsy demonstrated massive acute pulmonary embolism, which has not been previously reported in PS. In addition, clinically occult mesodermal hamartomata, predominantly hemolymphangiomata, were found to be widespread in the pelvoabdominal viscera, including spleen, appendix, kidneys, adrenal gland, liver, and retroperitoneal soft tissues. Such lesions may well be common in PS patients but may not be detected by conventional radiographic imaging techniques unless they are fairly large.