Diamond Blackfan Anemia: A Nonclassical Patient With Diagnosis Assisted by Genomic Analysis

Diamond Blackfan anemia (DBA) is an inherited syndrome usually presenting with severe macrocytic anemia in infancy, paucity of erythroid precursors in the bone marrow, and congenital anomalies. We describe a child with mild, transfusion independent normocytic anemia whose diagnosis of DBA was established by identification of a novel de novo mutation disrupting normal splicing of the ribosomal protein RPL5. The diagnosis of DBA was confirmed by elevated erythrocyte adenosine deaminase levels and an abnormal ribosomal RNA profile. This case demonstrates the usefulness of genomic analysis in establishing the diagnosis of DBA in patients with a nonclassical presentation of the disease

Whole-exome sequencing identifies an α-globin cluster triplication resulting in increased clinical severity of β-thalassemia

Whole-exome sequencing (WES) has been increasingly useful for the diagnosis of patients with rare causes of anemia, particularly when there is an atypical clinical presentation or targeted genotyping approaches are inconclusive. Here, we describe a 20-yr-old man with a lifelong moderate-to-severe anemia with accompanying splenomegaly who lacked a definitive diagnosis. After a thorough clinical workup and targeted genetic sequencing, we identified a paternally inherited β-globin mutation (HBB:c.93-21G>A, IVS-I-110:G>A), a known cause of β-thalassemia minor. As this mutation alone was inconsistent with the severity of the anemia, we performed WES. Although we could not identify any relevant pathogenic single-nucleotide variants (SNVs) or small indels, copy-number variant (CNV) analyses revealed a likely triplication of the entire α-globin cluster, which was subsequently confirmed by multiplex ligation-dependent probe amplification. Treatment and follow-up was redefined according to the diagnosis of β-thalassemia intermedia resulting from a single β-thalassemia mutation in combination with an α-globin cluster triplication. Thus, we describe a case where the typical WES-based analysis of SNVs and small indels was unrevealing, but WES-based CNV analysis resulted in a definitive diagnosis that informed clinical decision-making. More generally, this case illustrates the value of performing CNV analysis when WES is otherwise unable to elucidate a clear genetic diagnosis

Biallelic hypomorphic variants in CAD cause uridine-responsive macrocytic anaemia with elevated haemoglobin-A2

5 páginas, 2 figurasBiallelic pathogenic variants in CAD, that encode the multienzymatic protein required for de-novo pyrimidine biosynthesis, cause early infantile epileptic encephalopathy-50. This rare disease, characterized by developmental delay, intractable seizures and anaemia, is amenable to treatment with uridine. We present a patient with macrocytic anaemia, elevated haemoglobin-A2 levels, anisocytosis, poikilocytosis and target cells in the blood smear, and mild developmental delay. A next-generation sequencing panel revealed biallelic variants in CAD. Functional studies did not support complete abrogation of protein function; however, the patient responded to uridine supplement. We conclude that biallelic hypomorphic CAD variants may cause a primarily haematological phenotype.This work was supported by grant PID2021-128468NB-I00 financed by Ministerio de Ciencia e Innovación / Agencial Estatal de Investigación (MCIN/AEI) (https://www.aei.gob. es/) and by grant CIVP20A6610 from Fundación Ramón Areces Ciencias de la Vida (XX National Call) (https://www. fundacionareces.es) to SR-M. FdC-O is a postdoctoral fellow of the Generalitat Valenciana (Valencian Local Government) (https://www.gva.es/) (APOSTD 2021).Peer reviewe

Characterization and genotype-phenotype correlation of patients with Fanconi anemia in a multi-ethnic population

Fanconi anemia (FA), an inherited bone marrow failure (BMF) syndrome, caused by mutations in DNA repair genes, is characterized by congenital anomalies, aplastic anemia, high risk of malignancies and extreme sensitivity to alkylating agents. We aimed to study the clinical presentation, molecular diagnosis and genotype-phenotype correlation among patients with FA from the Israeli inherited BMF registry. Overall, 111 patients of Arab (57%) and Jewish (43%) descent were followed for a median of 15 years (range: 0.1-49); 63% were offspring of consanguineous parents. One-hundred patients (90%) had at least one congenital anomaly; over 80% of the patients developed bone marrow failure; 53% underwent hematopoietic stem-cell transplantation; 33% of the patients developed cancer; no significant association was found between hematopoietic stem-cell transplant and solid tumor development. Nearly 95% of the patients tested had confirmed mutations in the Fanconi genes FANCA (67%), FANCC (13%), FANCG (14%), FANCJ (3%) and FANCD1 (2%), including twenty novel mutations. Patients with FANCA mutations developed cancer at a significantly older age compared to patients with mutations in other Fanconi genes (mean 18.5 and 5.2 years, respectively, P=0.001); however, the overall survival did not depend on the causative gene. We hereby describe a large national cohort of patients with FA, the vast majority genetically diagnosed. Our results suggest an older age for cancer development in patients with FANCA mutations and no increased incidence of solid tumors following hematopoietic stem-cell transplant. Further studies are needed to guide individual treatment and follow-up programs

Syndromes predisposing to leukemia are a major cause of inherited cytopenias in children

Prolonged cytopenias are a non-specific sign with a wide differential diagnosis. Among inherited disorders, cytopenias predisposing to leukemia require a timely and accurate diagnosis to ensure appropriate medical management, including adequate monitoring and stem cell transplantation prior to the development of leukemia. We aimed to define the types and prevalences of the genetic causes leading to persistent cytopenias in children. The study comprises children with persistent cytopenias, myelodysplastic syndrome, aplastic anemia, or suspected inherited bone marrow failure syndromes, who were referred for genetic evaluation from all pediatric hematology centers in Israel during 2016-2019. For variant detection, we used Sanger sequencing of commonly mutated genes and a custom-made targeted next-generation sequencing panel covering 226 genes known to be mutated in inherited cytopenias; the minority subsequently underwent whole exome sequencing. In total, 189 children with persistent cytopenias underwent a genetic evaluation. Pathogenic and likely pathogenic variants were identified in 59 patients (31.2%), including 47 with leukemia predisposing syndromes. Most of the latter (32, 68.1%) had inherited bone marrow failure syndromes, nine (19.1%) had inherited thrombocytopenia predisposing to leukemia, and three each (6.4%) had predisposition to myelodysplastic syndrome or congenital neutropenia. Twelve patients had cytopenias with no known leukemia predisposition, including nine children with inherited thrombocytopenia and three with congenital neutropenia. In summary, almost one third of 189 children referred with persistent cytopenias had an underlying inherited disorder; 79.7% of whom had a germline predisposition to leukemia. Precise diagnosis of children with cytopenias should direct follow-up and management programs and may positively impact disease outcome

Congenital thrombocytopenia associated with a heterozygous variant in the MEIS1 gene encoding a transcription factor essential for megakaryopoiesis

The transcription factor MEIS1 (myeloid ectotrophic insertion site 1) is crucial for the maintenance of hematopoietic stem cells and for megakaryopoiesis. Germline variants in MEIS1 are associated with restless-leg syndrome, but were not previously shown to cause cytopenias. This is the first report of a patient with congenital thrombocytopenia associated with a sequence variant in MEIS1, presenting with early onset severe thrombocytopenia and mild signs of bone marrow stress. Whole exome sequencing revealed a de novo monoallelic splice site variant in MEIS1, NM_002398.3:exon4:c.432 + 5 G > C, leading to a premature stop codon. We propose that heterozygous mutations in MEIS1 may cause congenital thrombocytopenia

Codanin-1, the protein encoded by the gene mutated in congenital dyserythropoietic anemia type I (CDAN1), is cell cycle-regulated

Codanin-1 is a ubiquitous protein of unknown function, encoded by the gene mutated in congenital dyseritropoietic anemia type 1. The findings of this paper show that codanin-1 is active in S-phase of the cell cycle. See related perspective article on page 599