Prenatal Initiation of Therapy with mTOR Inhibitors for Giant Cardiac Rhabdomyoma

All articles of this category (opens in new window) Background: A 35-year-old IV. gravida III para presented to our tertiary center at 21 6/7 weeks of gestation because of an unclear intrathoracic mass. The ultrasound examination (including Doppler sonography) revealed a huge cardiac tumor originating from the myocardium of the left ventricular posterior wall. In addition, a moderate pericardial effusion was found. A giant cardiac rhabdomyoma was suspected. A molecular genetic diagnosis of tuberous sclerosis was rejected prenatally by the family. During regular follow-up, the intracardiac mass and the effusion were progressive in size up to a maximum diameter of 4.9 cm. Methods: We initiated maternal therapy with sirolimus at a target level of 10 to 15 ng/mL from 33 1/7 weeks of gestation. The drug therapy was well tolerated by the mother. The diagnosis was confirmed in an MRI scan at 35 weeks of pregnancy. Conclusion: By the time of birth at 40 4/7 weeks of gestation and a weight of 3,610 g, the effusion and tumor size had clearly decreased. The sirolimus level in the fetal cord blood was 5.4 ng/mL on the first day of life; a few days earlier, it was 11.6 ng/mL in maternal serum. Postnatally, we changed the immunosuppressive therapy in the newborn to everolimus with a target level of 5 to 15 ng/mL. A dose of 1 × 0.1 mg daily was initially selected for this purpose. The therapy was very well tolerated. There were no relevant side effects, in particular no serious infections or changes in the blood count. In the further course of treatment, the size of the tumor continued to decrease significantly, and tuberous sclerosis was confirmed in the child by molecular genetics. The NT-proBNP, which was significantly elevated at the age of 1 month, fell from 3,647 to 432 ng/L within a few weeks. Clinical development was unimpaired in the 1st year of life, both cardiac and neurological. Publication History Article published online: 17 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany