Alloimmune Thrombocytopenia: Tx and diagnosis. (Gamma Globulin Effective).

SARASOTA, FLA. -- Alloimmune thrombocytopenia is one of the true success stories in maternal-fetal medicine, Dr. Richard L. Berkowitz said at a symposium on high-risk pregnancy sponsored by Symposia Medicus.

Recent advances in maternal-fetal medicine have largely been in the area of diagnosis rather than treatment. "For most conditions [that] we now can diagnose in utero, our therapeutic options are very limited," he said.

Alloimmune thrombocytopenia is an important exception, however. "This is a devastating condition, which can cause death in utero or terrible long-term disability as a result of major intracranial bleeding, but in the overwhelming majority of cases we can successfully treat it medically" he said.

This disorder, in which the mother makes IgG antibodies to an incompatible platelet antigen that the fetus has inherited from the father, "is the platelet equivalent of Rh disease," said Dr. Berkowitz, professor and chairman of the department of obstetrics, gynecology and reproductive science, Mount Sinai Medical School, New York.

"In Rh disease, the typical sequence of events is that each pregnancy is tougher to manage than the one before. In this disease, it's often very bad with the first pregnancy. These are women not known to be at risk because we don't do routine antiplatelet antibody screening or antigen testing," he said.

The first indication of the disorder may be at birth, when petechiae are noted on the neonate. But in other cases, the mother may notice a diminution of fetal movement, and intracranial hemorrhage is found on ultrasound examination.

The mainstay of treatment is intravenous gamma globulin given to the mother, with or without low-dose dexamethasone. "We did a study in which we compared gamma globulin every week with gamma globulin plus dexamethasone because steroids also are beneficial in the treatment of this platelet disorder in newborns and in treating women with immune thrombocytopenia. What we found was that low-dose dexamethasone didn't add anything to the gamma globulin," Dr. Berkowitz said.