Fetal origins of hematopoietic failure in a murine model of Fanconi anemia.

Hematopoietic failure is the predominant clinical manifestation of Fanconi anemia (FA), a rare, recessively inherited disorder. Mutations in 1 of 15 genes that coordinately function in a complex pathway to maintain DNA integrity also predispose patients to constitutional defects in growth and development. The hematologic manifestations have been considered to reflect the progressive loss of stem cells from the postnatal bone marrow microenvironment. Ethical concerns preclude the study of human hematopoiesis in utero. We report significant late gestational lethality and profound quantitative and qualitative deficiencies in the murine Fancc(-/-) fetal liver hematopoietic stem and progenitor cell pool. Fancc(-/-) fetal liver hematopoietic stem and progenitor cells revealed a significant loss of quiescence and decline in serial repopulating capacity, but no substantial difference in apoptosis or levels of reactive oxygen species. Our studies suggest that compromised hematopoiesis in Fancc(-/-) animals is developmentally programmed and does not arise de novo in bone marrow.

Fanconi anemia with concurrent thumb polydactyly and dorsal dimelia: a case report with discussion of embryology.

Fanconi anemia is known to be associated with radial ray deficiency (thumb and radius hypoplasia), and its embryological basis remains to be poorly understood. We describe a rare case of Fanconi anemia with concurrent thumb polydactyly and dorsal dimelia. The embryological basis of limb abnormalities in Fanconi anemia patients is thought to be based on the complex interactions between the apical ectodermal ridge (where Fanconi anemia genes are expressed) and both the mesoderm (where Spalt-like 4 (SALL4) and Sonic hedgehog (SHH) are located and which are responsible for radial ray deficiency, thumb polydactyly, and triphalangism) and the dorsoventral axis (an error in that axis leads to dorsal dimelia).

Prenatal exclusion/confirmation of Fanconi anemia via flow cytometry: a pilot study.

OBJECTIVE: To explore the potential of flow cytometry in the prenatal exclusion or confirmation of Fanconi anemia (FA). METHODS: Indications for prenatal diagnosis were (1) FA-negative family history, but suspicious ultrasound findings such as radial ray aplasia, (2) FA-positive family history, but without knowledge of the affected gene and/or mutation. Amniotic fluid (AF) cell cultures and umbilical cord (UC) blood cultures were assayed for typical cell cycle changes (G2-phase accumulations) without and with mitomycin C (MMC) treatments using single- and dual-parameter (BrdU-Hoechst) flow cytometry. RESULTS: Single-parameter flow cytometry correctly identified 2 positive and 9 negative cases on the basis of MMC sensitivity of cultivated AF cells. Likewise, 8 negative and 2 positive cases were correctly predicted using bivariate flow cytometry of 72-hour UC blood cultures. In contrast, bivariate flow cytometry applied to AF cells grown in the presence of bromodeoxyuridine (BrdU) yielded false-positive and false-negative results. CONCLUSIONS: Single-parameter flow cytometry of AF cell cultures and bivariate flow cytometry of UC cell cultures have the potential to correctly predict the affected status in cases at risk for FA, whereas bivariate flow cytometry proved unreliable when applied to BrdU-substituted AF cell cultures. Cases with a low a priori risk (e.g. sonographic finding of radial ray abnormalities and negative family history) would benefit most from flow cytometry as a rapid and economical prenatal screening procedure.

Fanconi anemia associated with increased nuchal translucency detected by first-trimester ultrasound.

Increased nuchal translucency between 10 and 14 weeks of gestation has now been established as a marker for chromosomal defects in several large-scale studies. In addition, a growing number of structural defects and some rare genetic syndromes have been identified in association with this marker. We describe a case of a fetus with increased nuchal translucency at 12 weeks of gestation, in which second-trimester evaluation by ultrasound showed an enlarged cisterna magna, a ventricular septal defect and moderate signs of dysmorphia. Karyotyping by chorionic villus sampling revealed a high rate of chromosomal breaks. The diagnosis of Fanconi anemia with early onset was confirmed following the development of severe postnatal anemia 2 months after birth.

Abnormal motor behaviour and developmental postmortem findings in a fetus with Fanconi anaemia.

Prenatal diagnosis in the third pregnancy of a mother who already had one healthy son and one son with Fanconi anaemia (FA), revealed that her fetus was also affected with FA. At 22 weeks a maternal complaint about excessive fetal kicking starting at 15 weeks, focused our attention on the behaviour of the fetus, which was observed by means of real-time ultrasound for 30 min. The differentiation of specific movement patterns was strongly diminished. The qualitative expression of general movements was considered to be consistently abnormal due to the fact that they were performed with large amplitudes, high speed and abrupt onsets. The incidence of general movements was within the normal range, however, the distribution in the burst-pause pattern was abnormal. Postmortem examination showed a spongy myelinopathy of the central nervous system that may account for the abnormal motor activity. This combination of findings has not been previously reported in association with FA.

Umbilical cord blood transplants for genetic disease: diagnostic and ethical issues in fetal studies.

A variety of genetic disorders are treatable by allogeneic bone marrow transplantation. Predictive genetic testing and HLA typing of cultured fetal cells enable one to know early in a pregnancy that a fetus is genetically normal and is HLA-identical to a sibling affected with a genetic disease. Umbilical cord blood can be collected at the delivery of an HLA-matched normal sibling and used for stem/progenitor cell transplantation for the affected child. Our experience with families of children with Fanconi anemia has shown that the deliberate conception of a fetus for the possibility of providing a transplant donor is often undertaken. This paper reviews the genetic diseases potentially treatable by cord blood transplantation and the methods and pitfalls of prenatal testing for these conditions. Our laboratory's extensive experience with prenatal diagnosis for Fanconi anemia is discussed and provides the framework for an examination of the ethical issues related to the conception of a fetus for the purpose of providing a transplant donor.

Diamond-Blackfan anemia associated with Treacher-Collins syndrome.

We describe a 2-year-old girl with a rare combination of congenital red cell aplasia or Diamond-Blackfan anemia (DBA) and Treacher-Collins syndrome (TCS). The anemia is only marginally responsive to high-dose corticosteroid, and the child is transfusion dependent. There is no one in the family affected with either DBA or TCS. A hypothesis is advanced that the simultaneous occurrence of the dysmorphism and erythroid agenesis in this case may have been the consequences of an insult to the fetus at the critical stage of development of maxillomandibular structure and the stage of primitive erythroid cell migration from the yolk sac to the fetal liver and bone marrow.

Temporal bone histopathologic features in Fanconi's anemia syndrome.

A histopathologic study of the temporal bones from a 7-year-old girl with Fanconi's anemia syndrome demonstrated (1) hemorrhage in the submucosal layer and the cavity of the middle ear and mastoid, massive in the right ear; (2) hypocellularity of the bone marrow; (3) minor but multiple anomalies of the middle ear; and (4) hypodevelopment of the hook portion of the cochlea and reduced overall length of the cochlear duct. The histopathologic features of these temporal bones appears to suggest that congenital anomalies of the inner ear, as well as those of the external and middle ears, would be possible causes of the deafness that accompanies Fanconi's anemia syndrome.