Prenatal diagnosis of Klippel–Trenaunay–Weber syndrome with Kasabach–Merritt syndrome in utero

Klippel - Trenaunay - Weber syndrome (KTWS), a congenital disease characterized by cutaneous hemangiomas, soft tissue and bone hypertrophy, and occasionally arteriovenous malformations, is extremely rare and its natural history in utero is unknown. We present a prenatally diagnosed case of KTWS complicated with Kasabach - Merritt syndrome in utero and fetal hydrops from acute anemia. The fetus was diagnosed with KTWS at 24 weeks of gestation based on the ultrasound findings of hemangiomas and unilateral hypertrophy of the lower extremity. Acute enlargement of the hemangiomas and the appearance of new retroperitoneal hemangiomas were detected at 27 weeks, along with skin edema and cardiomegaly. Doppler examination showed elevated peak systolic velocity in the middle cerebral artery, indicating acute fetal anemia. We believe the fetus’s condition was complicated with Kasabach - Merritt syndrome in utero, which caused acute hemolytic anemia leading to high-output cardiac failure and fetal hydrops.