glucose-6-phosphate isomerase ( gpi ) deficiency is the third most common red blood cell enzymopathy , after glucose-6-phosphate dehydrogenase ( g6pd ) and pyruvate kinase ( pk ) deficiency and is similarly associated with hereditary nonspherocytic hemolytic anemia ( hnsha ) . the sole clinical manifestation in the majority of patients is chronic hsnha , ranging from mild to severe . most cases of gpi deficiency are diagnosed during the neonatal and childhood period . to date , only two cases of prenatal diagnosis of gpi deficiency have been reported . additionally , cases of postnatal diagnoses of hydrops caused by gpi deficiency were documented , usually without survival of the affected child 2,3 . in this case report , we describe a family in which two siblings have congenital hsnha due to gpi deficiency . the first child was diagnosed at the age of 3  years , the second was monitored antenatally with repeated doppler ultrasound and was eventually treated for fetal anemia with repeated intrauterine transfusions . to our knowledge , this is the first case of prenatal diagnosis of gpi deficiency in cord blood , followed by successful intrauterine treatment of gpi - deficient fetal anemia . a 33-year - old woman was referred to our center at 17  weeks of gestation because of an increased risk of fetal anemia . their first child , a 5-year - old girl , was born after an uneventful pregnancy and did not suffer from extreme neonatal jaundice or anemia . she was diagnosed with gpi deficiency at the age of 3  years after her first documented acute hemolytic episode with signs of jaundice , severe anemia , and hemoglobinuria . following extensive investigation dna analysis showed the girl to be homozygous for the c.1615g > a , p.(asp539asn ) missense mutation in gpi . both the mother and father were found to be heterozygous for the same mutation . at present , the girl remains clinically well , has normal growth and neuropsychological development but has evident chronic hemolysis treated with folic acid . she has had infrequent exacerbations of hemolysis associated with minor childhood infections but nonsevere enough to warrant erythrocyte transfusions . the current pregnancy was the fourth pregnancy of this couple , following two early miscarriages . the parents refrained from early diagnostic chorionic villus biopsy or amniocentesis ( because of the risk of miscarriage ) , but instead opted for ultrasound monitoring for signs of fetal anemia ( measurement of the mca doppler peak systolic velocity ( mca - psv ) ) . the pregnancy was followed up on a weekly basis , from 16  weeks of gestation onward . at 26  weeks of gestation , fetal anemia was suspected , based on an increased mca - psv of > 1.5 multiples of the median ( mom ) ( fig.1 ) . there is suspicion of fetal anemia when vmax in the middle cerebral artery exceeds 1.5  mom . the first iut was given transplacentally in the umbilical cord root at 27  weeks of gestation . pretransfusion cord blood was obtained for diagnostic testing , the fetal hemoglobin level was 7.4  g / dl . an uncomplicated intravenous transfusion of donor blood was performed , resulting in a posttransfusion hemoglobin concentration of 13.5  g / dl . genetic analysis of fetal cells confirmed that the second child was also homozygous for the aforementioned mutations in the gpi gene . after the diagnosis was made , folic acid was prescribed to the mother in a daily dosage of 5  mg . another two iut 's were performed at gestational weeks 30 and 34 ( table1 ) . based on the fact that the fetus needed repetitive intrauterine transfusions from 27  weeks of gestation onwards , labor was induced at 37  weeks to avoid further intrauterine transfusions . a girl was born vaginally with apgar scores of 9 and 10 at 1 and 5  min , respectively . the cord blood ph was 7.25 and her weight was 3620  g. neonatal jaundice was apparent immediately after birth . the child required no exchange or top - up transfusions and was discharged at day 7 . at 4  weeks of age , despite resolving hemolytic parameters ( decreasing bilirubin and ldh ) the girl remained reticulocytopenic and required an additional blood transfusion for symptomatic anemia . two weeks after transfusion , spontaneous recovery of hemoglobin concentration was observed , with rising reticulocytes ( 105    10/l ) , normal bilirubin ( 11  mol / l ) , normal ldh ( 241  u / l ) , and low haptoglobin ( < 0.1 she remains well and transfusion - independent at the current age of 5  months , while receiving folic acid replacement therapy . intrauterine transfusion data for the treatment of fetal anemia volume transfused : volume of transfused red blood cells . gpi is a dimeric enzyme which catalyzes the reversible conversion of glucose-6-phosphate and fructose-6-phosphate , the second step in glycolysis . the gpi gene is located on the long arm of chromosome 19 and 31 mutations in the gpi gene are currently listed in the human gene mutation database ( www.hgmd.cf.ac.uk ) . the majority of these mutations are missense mutations affecting key interactions of the enzyme 's active site 5 . gpi - deficient patients are either homozygous or compound heterozygous for such mutations , and are clinically characterized by chronic hemolytic anemia with hemolytic crises during infection or after ingestion of hemolytic drugs 6 . the current therapy consists of blood transfusions and splenectomy for the most severe hemolytic cases 3,7 . it has been suggested that mutant gpi is inactivated faster with increasing rbc cell age than the wild - type enzyme 8 . the manifestation in affected fetuses might therefore be milder because of the shorter lifespan of fetal rbcs . however , if fetal hydrops develops due to gpi deficiency , the prognosis is usually very poor 2,9 . in the literature , performed the first prenatal gpi deficiency diagnosis at 28  weeks of gestation by assessing the gpi characteristics in amniotic fluid cells . gpi deficiency was considered after the neonatal death of a previous child with hydrops . the second child in this family was diagnosed antenatally as compound heterozygous for two different mutant gpi alleles and received an exchange transfusion after birth , which took place at 35  weeks of gestation 2 . provided a first trimester gpi deficiency diagnosis on trophoblast cells obtained from chorionic villus sampling 1 . in the present case , instead , close fetal surveillance by ultrasound scanning was performed on a weekly basis , to monitor for signs of fetal anemia . the diagnosis was confirmed by genetic analysis of dna of cord blood cells , sampled before the first iut . iut is universally accepted as an efficient treatment for fetal anemia . in the leiden university medical center , serving as the dutch national referral center for fetal therapy since 1965 , it was the first time iuts were performed for fetal anemia due to gpi deficiency . we prescribed folic acid supplementation to the mother to prevent the occurrence of megaloblastic anemia in the fetus . postdelivery the girl also received folic acid , as is standard in patients with  hemolytic anemia . this is a well - known phenomenon in children that received intrauterine transfusions and is thought to be induced by reduction in their own erythropoietin production . the parents are both heterozygous for both mutations suggesting that although they were reported to be nonconsanguineous it is very likely that they stem from a common ancestor . one possibility could be early exposure to oxidant agents which can trigger episodes of hemolysis . however , obstetric history of the second pregnancy showed no infection or known ingestion of oxidant drugs or food . whitelaw et  al . also reported a family of two affected siblings with different disease severity 2 . pointed out that patients with the same mutation and deficient gpi activity can present with varying degrees of anemia and clinical impairment 7 . our findings confirm that the hemolytic episodes caused by gpi deficiency are unpredictable and emphasize the importance of prenatal monitoring of fetuses at risk . in conclusion , hemolytic anemia due to gpi deficiency can be severe and life threatening during fetal life . we recommend frequent ultrasound monitoring for prenatal management of pregnancies in which there is an increased risk of fetal gpi deficiency , when parents decline early invasive testing . in this case , repeated intrauterine blood transfusions appeared to be effective for the treatment of severe fetal anemia due to gpi deficiency and may additionally have prevented the development of fetal hydrops and demise .
key clinical messagehemolytic anemia due to gpi deficiency can be severe and life threatening during fetal life . 
 when parents decline invasive testing , ultrasound monitoring of fetuses at risk is feasible . 
 intrauterine transfusion can be effective for the treatment of severe fetal anemia due to gpi deficiency .