Fetal hemochromatosis: rare case of hepatic and extrahepatic siderosis involving thyroid on fetal MRI

Neonatal hemochromatosis (NH) is a rare condition that is characterized by severe neonatal liver disease in association with hepatic and extrahepatic excess iron deposition (siderosis), while sparing the reticuloendothelial system. The most common cause of fetal liver injury leading to the NH phenotype (accounting for over 95% of cases) is gestational alloimmune liver disease. This condition is caused by the transfer of maternal IgG antibodies through the placenta, targeting a fetal hepatocyte antigen. Prenatal diagnosis, particularly the identification of iron overload involving both liver and thyroid, is of significant importance and can have a profound impact on patient care. To our knowledge, no case has been reported on prenatal diagnosis of iron overload involving both liver and thyroid. We present an exceptionally rare case of fetal hemochromatosis in a primigravida, a case that significantly contributes to our understanding of this condition. The diagnosis was made with the presence of hepatic and extrahepatic siderosis involving the thyroid using Ultrasonography (USG) and fetal Magnetic Resonance Imaging (MRI) findings. A 23-year-old primigravida was referred to our center in view of oligohydramnios, Intrauterine Growth Restriction (IUGR) and echogenic bowel at 29 weeks of gestation. USG and fetal MRI showed features of coarse liver echotexture and iron overload involving the liver and thyroid; this is the first case describing iron accumulation in the fetal thyroid gland diagnosed in utero. This case underscores the critical importance of performing MRI in suspected cases of fetal hemochromatosis for early diagnosis and intervention, emphasizing the potential to significantly improve patient outcomes.