Complexities of genetic diagnosis illustrated by an atypical case of congenital hypoplastic anemia.

Diamond-Blackfan Anemia (DBA) is a rare polygenic disorder defined by congenital hypoplastic anemia with marked decrease or absence of bone marrow erythroid precursors. Identifying the specific genetic etiology is important for counseling and clinical management. A 6-yr-old boy with a clinical diagnosis of DBA has been followed by our pediatric hematology team since birth. His clinical course includes transfusion-dependent hypoplastic anemia and progressive autoimmune cytopenias. Genetic testing failed to identify a causative mutation in any of the classical DBA-associated genes. He and his parents underwent trio whole-exome sequencing (WES) with no genetic etiology identified initially. Clinical persistence and suspicion led to testing for adenosine deaminase 2 (ADA2) activity and whole-genome sequencing (WGS) that identified compound heterozygous pathogenic mutations in the ADA2-encoding CECR1 gene, a recently appreciated etiology for congenital hypoplastic anemia. This case illustrates current challenges in genetic testing and how they can be overcome by multidisciplinary expertise in clinical medicine and genomics.

Congenital hypoplastic bone marrow failure associated with a de novo partial deletion of the MECOM gene at 3q26.2.

Congenital hypoplastic bone marrow failure is a rare condition in neonates. The genetics and mechanisms behind are largely obscure. Here we characterize a neonate presenting with congenital thrombocytopenia and anemia. During the first 2-4 weeks after birth the neonate developed severe neutropenia while the lymphoid lineages were unaffected. The neonate was without dysmorphic signs. A de novo mono-allelic constitutional microdeletion of 175.1 kb at 3q26.2 affecting exon 2 of MECOM, involving MDS1 but not EVI1, was identified as the only copy number alteration by oligo-based array-CGH analysis. Expression analysis showed profoundly reduced expression of multiple MECOM transcripts in the bone marrow cells. Whole exome sequencing detected no pathogenic mutations in genes known to be associated with inherited bone marrow failure syndromes. The patient was successfully treated with hematopoietic stem cell transplantation at 5 months of age. Interstitial deletions encompassing the 3q26.2 region are very rare. A literature search revealed two previous cases with microdeletions involving this region, and the cases were associated with congenital thrombocytopenia and anemia, but unaffected lymphopoiesis. Together these data indicate that MECOM may be important for normal myeloid hematopoiesis in humans but dispensable for lymphoid differentiation. We suggest that partial deletion in MECOM may be a primary event associated with congenital pancytopenia.

In vitro generated Rh(null) red cells recapitulate the in vivo deficiency: a model for rare blood group phenotypes and erythroid membrane disorders.

Lentiviral modification combined with ex vivo erythroid differentiation was used to stably inhibit RhAG expression, a critical component of the Rh(rhesus) membrane complex defective in the Rh(null) syndrome. The cultured red cells generated recapitulate the major alterations of native Rh(null) cells regarding antigen expression, membrane deformability, and gas transport function, providing the proof of principle for their use as model of Rh(null) syndrome and to investigate Rh complex biogenesis in human primary erythroid cells. Using this model, we were able to reveal for the first time that RhAG extinction alone is sufficient to explain ICAM-4 and CD47 loss observed on native Rh(null) RBCs. Together with the effects of RhAG forced expression in Rh(null) progenitors, this strongly strengthens the hypothesis that RhAG is critical to Rh complex formation. The strategy is also promising for diagnosis purpose in order to overcome the supply from rare blood donors and is applicable to other erythroid defects and rare phenotypes, providing models to dissect membrane biogenesis of multicomplex proteins in erythroid cells, with potential clinical applications in transfusion medicine.

Neutrophil functions in patients with inherited bone marrow failure syndromes.

BACKGROUND: The inherited bone marrow failure syndromes (IBMFS) include Fanconi anemia, dyskeratosis congenita, Diamond-Blackfan anemia, and Shwachman-Diamond syndrome (SDS). Previous studies reported decreased neutrophil chemotaxis in patients with SDS; there are no reports of neutrophil function in other IBMFS. In this study we examined neutrophil respiratory burst function in IBMFS patients. PROCEDURE: Samples from 43 IBMFS patients and 61 healthy family members were collected, shipped, and analyzed within 24 hr. We also studied samples from 12 healthy control persons immediately after collection. Neutrophils were stimulated with phorbol 12-myristate acetate (PMA) and N-formyl-methyonyl-leucyl-phenylalanine (fMLP), and respiratory burst analyzed by reduction of dihydro-rhodamine and cytochrome c. RESULTS: There was no significant difference in the degree of fMLP or PMA-driven respiratory burst activity between each of the IBMFS subgroups and their respective family members. There was also no difference in respiratory burst activity between any IBMFS, pooled group of all healthy family members and healthy controls. CONCLUSIONS: Neutrophil respiratory burst activity from IBMFS patients does not differ from that of healthy family members and controls.

Hematopoietic stem cell transplantation in childhood inherited bone marrow failure syndrome.

Aplastic anemia is a rare disease in children that is most commonly idiopathic and less often a hereditary disorder. Hereditary bone marrow failure (BMF) syndromes, however, should be considered both in children and in adults before any attempt at treatment. Precise diagnosis is important because it will modify prognostic treatment options and the results of bone marrow transplantation. In this review, we will report recent results of treatment of Fanconi anemia and other hereditary BMF syndromes.

Reduced intensity hematopoietic stem-cell transplantation across human leukocyte antigen barriers in a patient with congenital amegakaryocytic thrombocytopenia and monosomy 7.

Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare inherited bone marrow failure syndrome that has the potential to progress to pancytopenia and acute myeloid leukemia. Hematopoietic stem-cell transplantation (HSCT) is presently the only curative treatment approach. We used a reduced intensity transplantation regimen in a CAMT patient with aplastic anemia and monosomy 7 who had no matched related donor. The patient had rapid and durable engraftment with minimal complications and is well 24 months post-transplantation. Thus, reduced intensity conditioning might be a feasible approach to stem-cell transplantation in patients with CAMT who do not have a related donor and who are at increased risk of toxicity from standard conditioning regimens.

Anesthetic management of Cesarean delivery in a patient with hypoplastic anemia and severe pre-eclampsia.

PURPOSE: To describe the anesthetic management of Cesarean delivery in a patient with hypoplastic anemia and severe pre-eclampsia. CLINICAL FEATURES: A 28-yr-old parturient with a history of thrombocytopenia was admitted with signs of pre-eclampsia (blood pressure of 140/90 mmHg, heavy proteinuria and moderate bilateral ankle edema) at 25 weeks of gestation. Laboratory studies revealed pancy-topenia (hemoglobin 6.4 g.dL(-1), white cell count 3.43 x 10(9).L(-1), platelet count 20 x 10(9).L(-1)) and bone marrow biopsy showed hypoplastic anemia. As pre-eclampsia worsened, a Cesarean delivery was performed at 27 weeks with prophylactic platelet transfusion and meticulous blood pressure control. The procedure was uneventful, conducted under general anesthesia with an estimated blood loss of around 600 mL and a live female baby was delivered. Postoperatively her blood pressure and neurological symptoms improved but thrombocytopenia remained at discharge. CONCLUSIONS: Hypoplastic anemia is rare in pregnancy but it poses an increased risk for both mother and fetus. The mother is at risk of life-threatening episodes of bleeding and infection and a multidisciplinary team approach (obstetrician, anesthesiologist, hematologist and pediatrician) is essential. An accurate assessment of the hematological condition should be made and abnormalities corrected before surgery. Regional anesthesia may not be possible in this circumstance.

Differential diagnosis and management of anemia in the newborn.

Neonatal anemia is a condition with a diverse etiologic spectrum.Therefore, in order to form a focused differential diagnosis, it is important for the caregiver to have some knowledge of the more common causes of low hemoglobin and hematocrit concentrations in the neonate. Proper history taking, physical examination, and interpretation of diagnostic tests can narrow this focus and aid in establishing an accurate diagnosis and in directing the appropriate therapeutic interventions.