Frequency and natural history of inherited bone marrow failure syndromes: the Israeli Inherited Bone Marrow Failure Registry

BACKGROUND

Inherited bone marrow failure syndromes are rare genetic disorders characterized by bone marrow failure, congenital anomalies, and cancer predisposition. Available single disease registries provide reliable information regarding natural history, efficacy and side effects of treatments, and contribute to the discovery of the causative genes. However, these registries could not shed light on the true incidence of the various syndromes. We, therefore, established an Israeli national registry in order to investigate the relative frequency of each of these syndromes and their complications.

DESIGN AND METHODS

Patients were registered by their hematologists in all 16 medical centers in Israel. We included patients with Fanconi anemia, severe congenital neutropenia, Diamond-Blackfan anemia, congenital amegakaryocytic thrombocytopenia, dyskeratosis congenita, Shwachman-Diamond syndrome, and thrombocytopenia with absent radii.

RESULTS

One hundred and twenty-seven patients diagnosed between 1966 and 2007 were registered. Fifty-two percent were found to have Fanconi anemia, 17% severe congenital neutropenia, 14% Diamond-Blackfan anemia, 6% congenital amegakaryocytic thrombocytopenia, 5% dyskeratosis congenita, 2% Shwachman-Diamond syndrome, and 2% thrombocytopenia with absent radii. No specific diagnosis was made in only 2 patients. Of the thirty patients (24%) developing severe bone marrow failure, 80% had Fanconi anemia. Seven of 9 patients with leukemia had Fanconi anemia, as did all 6 with solid tumors. Thirty-four patients died from their disease; 25 (74%) had Fanconi anemia and 6 (17%) had severe congenital neutropenia.

CONCLUSIONS

This is the first comprehensive population-based study evaluating the incidence and complications of the different inherited bone marrow failure syndromes. By far the most common disease was Fanconi anemia, followed by severe congenital neutropenia and Diamond-Blackfan anemia. Fanconi anemia carried the worst prognosis, with severe bone marrow failure and cancer susceptibility. Diamond-Blackfan anemia had the best prognosis. The data presented provide a rational basis for prevention programs and longitudinal surveillance of the complications of inherited bone marrow failure syndromes.

Inherited thrombocytopenia associated with mutation of UDP-galactose-4-epimerase (GALE)

Severe thrombocytopenia, characterized by dysplastic megakaryocytes and intracranial bleeding, was diagnosed in six individuals from a consanguineous kindred. Three of the individuals were successfully treated by bone marrow transplant. Whole-exome sequencing and homozygosity mapping of multiple family members, coupled with whole-genome sequencing to reveal shared non-coding variants, revealed one potentially functional variant segregating with thrombocytopenia under a recessive model: GALE p.R51W (c.C151T, NM_001127621). The mutation is extremely rare (allele frequency = 2.5 × 10-05), and the likelihood of the observed co-segregation occurring by chance is 1.2 × 10-06. GALE encodes UDP-galactose-4-epimerase, an enzyme of galactose metabolism and glycosylation responsible for two reversible reactions: interconversion of UDP-galactose with UDP-glucose and interconversion of UDP-N-acetylgalactosamine with UDP-N-acetylglucosamine. The mutation alters an amino acid residue that is conserved from yeast to humans. The variant protein has both significantly lower enzymatic activity for both interconversion reactions and highly significant thermal instability. Proper glycosylation is critical to normal hematopoiesis, in particular to megakaryocyte and platelet development, as reflected in the presence of thrombocytopenia in the context of congenital disorders of glycosylation. Mutations in GALE have not previously been associated with thrombocytopenia. Our results suggest that GALE p.R51W is inadequate for normal glycosylation and thereby may impair megakaryocyte and platelet development. If other mutations in GALE are shown to have similar consequences, this gene may be proven to play a critical role in hematopoiesis.

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

BACKGROUND

Congenital dyserythropoietic anemia type I is an inherited autosomal recessive macrocytic anemia associated with ineffective erythropoiesis and the development of secondary hemochromatosis. Distinct erythroid precursors with internuclear chromatin bridges and spongy heterochromatin are pathognomonic for the disease. The mutated gene (CDAN1) encodes a ubiquitously expressed protein of unknown function, codanin-1. Based on the morphological features of congenital dyserythropoietic anemia type I erythroblasts and data on a role in cell cycle progression of codanin-1 homolog in Drosophila we investigated the cellular localization and possible involvement of codanin-1 during the cell cycle.

DESIGN AND METHODS

Codanin-1 localization was studied by immunofluorescence and immune electron microscopy. Cell cycle expression of codanin-1 was evaluated using synchronized HeLa cells. E2F proteins are the main regulator of G(1)/S transition. An E2F1-inducible cell line (U20S-ER-E2F1) enabled us to study codanin-1 expression following ectopic E2F1 induction. Direct binding of E2F1 to codanin-1 promoter was assessed by chromatin immunoprecipitation. We used a luciferase-reporter plasmid to study activation of CDAN1 transcription by E2F1.

RESULTS

We localized codanin-1 to heterochromatin in interphase cells. During the cell cycle, high levels of codanin-1 were observed in the S phase. At mitosis, codanin-1 underwent phosphorylation, which coincided with its exclusion from condensed chromosomes. The proximal CDAN1 gene promoter region, containing five putative E2F binding sites, was found to be a direct target of E2F1.

CONCLUSIONS

Taken together, these data suggest that codanin-1 is a cell cycle-regulated protein active in the S phase. The exact role of codanin-1 during the S phase remains to be determined. Nevertheless this represents the first step towards understanding the function of the proteins involved in congenital dyserythropoietic anemia.

Targeted next generation sequencing for the diagnosis of patients with rare congenital anemias

BACKGROUND

Most patients with anemia are diagnosed through clinical phenotype and basic laboratory testing. Nonetheless, in cases of rare congenital anemias, some patients remain undiagnosed despite undergoing an exhaustive workup. Genetic testing is complicated by the large number of genes involved in rare anemias and the similarities in the clinical presentation of the different syndromes.

OBJECTIVE

We aimed to enhance the diagnosis of patients with congenital anemias by using targeted next-generation sequencing.

METHODS

Genetic diagnosis was performed by gene capture followed by next-generation sequencing of 76 genes known to cause anemia syndromes.

RESULTS

Genetic diagnosis was achieved in 13 out of 21 patients (62%). Six patients were diagnosed with pyruvate kinase deficiency, 4 with dehydrated hereditary stomatocytosis, 2 with sideroblastic anemia, and 1 with CDA type IV. Eight novel mutations were found. In 7 patients, the genetic diagnosis differed from the pretest presumed diagnosis. The mean lag time from presentation to diagnosis was over 13 years.

CONCLUSIONS

Targeted next-generation sequencing led to an accurate diagnosis in over 60% of patients with rare anemias. These patients do not need further diagnostic workup. Earlier incorporation of this method into the workup of patients with congenital anemia may improve patients' care and enable genetic counseling.

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.

Genetic analysis and clinical picture of severe congenital neutropenia in Israel

BACKGROUND

The relative frequency of mutated genes among patients with severe congenital neutropenia (SCN) may differ between various ethnic groups. To date, few population-based genetic studies have been reported. This study describes the genetic analysis of 32 Israeli patients with SCN.

PROCEDURES

Clinical data were retrieved from the prospective Israeli Inherited Bone Marrow Failure Registry. Recruitment included living and deceased patients who were diagnosed between 1982 and 2012, for whom molecular diagnosis was performed. ELANE, HAX1 and G6PC3 genes were sequenced in all patients, and GFI-1 and WAS genes were sequenced if other genes were wildtype.

RESULTS

Eleven patients (34%) had heterozygous mutations in ELANE (10 kindreds), eight (25%) had homozygous mutations in G6PC3 (5 kindreds) and 13 (41%) had no detected mutations. No patients had mutations in HAX1 or WAS. Four of the eight patients with G6PC3 mutations had congenital anomalies. The probability of survival for all patients was 50% at age of 18. Deaths were mainly due to sepsis (5 patients, 4/5 not responding to G-CSF, none with G6PC3 mutation). Two patients developed acute myelogenous leukemia (AML) and one myelodysplastic syndrome (MDS), none with G6PC3 mutation.

CONCLUSIONS

We found a unique pattern of SCN mutations in Israel with homozygous G6PC3 mutations in eight (25%) patients, the highest frequency described so far. HAX1 mutations, reported mainly in Sweden and Iran, were absent. Patients with G6PC3 mutations had congenital anomalies, appeared to have a better response to G-CSF, and so far have not developed AML or MDS.

E109K is a SEC23B founder mutation among Israeli Moroccan Jewish patients with congenital dyserythropoietic anemia type II

OBJECTIVE

Congenital dyserythropoietic anemia (CDA) is characterized by ineffective erythropoiesis, binuclearity of erythroid precursors and secondary hemochromatosis. Recently, the gene mutated in CDA type II (CDA II), SEC23B, was identified. All Israeli patients with CDA II are of North African (mainly Moroccan) Jewish descent. We investigated the molecular basis of CDA II in those patients.

METHODS

Participants included 11 patients with CDA II from 8 apparently unrelated families. Clinical data were retrieved from medical files, and blood was collected for DNA analysis.

RESULTS

The majority of patients (10/11) were homozygous for a common SEC23B mutation (E109K). Haplotype analysis revealed a common genetic background in all patients. One patient was a compound heterozygote for the E109K mutation and a novel mutation, T710M. All patients were transfusion independent, with increasing iron overload with age. We estimate the E109K mutation to be 2,400 years old, in line with Jewish migration history.

CONCLUSIONS

Most CDA II patients in Israel are of Moroccan Jewish origin and carry a common SEC23B mutation, E109K, the first to be described as a founder mutation causing CDA II. As previously suggested, carrying 2 missense mutations is associated with a relatively nonsevere phenotype.

Congenital dyserythropoietic anaemia, type I, in a Caucasian patient with retinal angioid streaks (homozygous Arg1042Trp mutation in codanin-1)

A congenital dyserythropoietic anaemia (CDA) was recognised in a French Caucasian male patient. Blood smears showed a pronounced aniso-poikilocytosis. Bone marrow light microscopy showed signs of dyserythropoesis, but no internuclear chromatin bridges. Electron microscopy disclosed erythroblast nuclei with the Swiss cheese aspect and the presence of cytoplasmic organelles, assessing the diagnosis of CDA I. The presence of internuclear chromatin bridges may thus be missing in CDA I. The patient proved to be homozygous for the Arg1042Trp mutation in codanin-1 (the 'Bedouin mutation'). By the age of 25, the patient's vision started to deteriorate as a result of retinal angioid streaks and macular abnormalities. Evolution was controlled and the patient, being nearly 50 yr old now, still has a partial use of his eyes. This second case of retinal angioid streaks reported in CDA I adds to the non-haematological features likely to be associated with this condition.

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.

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.

Incorporation of somatic panels for the detection of haematopoietic transformation in children and young adults with leukaemia predisposition syndromes and with acquired cytopenias

Detection of somatic mutations may help verify the diagnosis of myelodysplastic syndrome (MDS) in patients with persistent cytopenias or with MDS-predisposition syndromes, prior to the development of overt leukemia. However, the spectrum and consequences of acquired changes in paediatric patients have not been fully evaluated, and especially not in the context of an underlying syndrome. We incorporated a targeted next-generation-sequencing panel of 54 genes for the detection of somatic mutations in paediatric and young adult patients with inherited or acquired cytopenias. Sixty-five patients were included in this study, of whom 17 (26%) had somatic mutations. We detected somatic mutations in 20% of individuals with inherited MDS-predisposition syndromes, including in patients with severe congenital neutropenia and Fanconi anaemia, and with germline mutations in SAMD9L. Thirty-eight per cent of children with acquired cytopenias and suspected MDS had somatic changes, most commonly in genes related to signal transduction and transcription. Molecularly abnormal clones often preceded cytogenetic changes. Thus, routine performance of somatic panels can establish the diagnosis of MDS and determine the optimal timing of haematopoietic stem cell transplantation, prior to the development of leukaemia. In addition, performing somatic panels in patients with inherited MDS-predisposition syndromes may reveal their unique spectrum of acquired mutations.

Endoscopic findings and esophageal cancer incidence among Fanconi Anemia patients participating in an endoscopic surveillance program

BACKGROUND AND AIMS

The primary clinical characteristics of Fanconi Anemia (FA) include typical physical features, progressive bone marrow failure, and an increased incidence of neoplasms, including esophageal carcinoma. Currently, there are no data regarding endoscopic findings or the interval time to malignancy in these patients. Data about the contribution of Human Papilloma Virus (HPV) to esophageal carcinoma is conflicting. Our objective is to document the upper gastrointestinal (GI) findings at baseline, document cancer incidence, and evaluate the role of HPV among these cancers.

METHODS

We reviewed endoscopic and clinical data of FA subjects who participated in active surveillance before cancer diagnosis. Incident esophageal cancers were stained for HPV ^p16 protein.

RESULTS

Eight FA patients were included (men 62.5%; median age at first endoscopy 20 years, median endoscopies number: 5.5). At baseline, 8/8 had endoscopic evidence for reflux esophagitis. In 3/8 the reflux esophagitis was mild and in 5/8 it was moderate or severe. During the follow up time (median time 4.5 years 2/8 developed Barrett's esophagus and 2/8 patients had incident esophageal squamous cell carcinoma during follow up, at intervals of eight and eighteen months from the previous upper endoscopy. Both cancers stained negative for HPV ^P16.

CONCLUSIONS

FA subjects have both an extremely high risk for esophageal cancer within short intervals and a very high prevalence of reflux esophagitis with various severities. Active surveillance programs in specialized centers including annual upper endoscopies should be considered in these patients.

Small-platelet thrombocytopenia in a family with autosomal recessive inheritance pattern

We describe the clinical and laboratory features of a family of Arab ancestry and consanguinity. Five affected individuals were diagnosed in two sibships. All affected members have small platelets, severe to moderate thrombocytopenia of neonatal onset, increased bleeding tendency and bleeding complications such as: life-threatening massive hemoperitoneum due to corpus luteum rupture during ovulation and severe mucosal bleeding. The familial involvement and early onset of the disease support the presence of a congenital genetic disorder with an autosomal recessive inheritance pattern. This does not fit the clinical spectrum of any of the currently known thrombocytopenia disorders.

Alpha-Thalassemia Carrier due to -α3.7 Deletion: Not So Silent

BACKGROUND/OBJECTIVE

Alpha-thalassemia is one of the most prevalent genetic diseases, with the -α3.7 deletion being the most common mutation. Molecular studies have suggested mechanisms to explain the mild phenotype of "silent carrier" heterozygotes. However, the correlation between the clinical laboratory picture and the -α3.7 heterozygous state remains unclear, thus we chose to investigate.

METHODS

We analyzed the medical files of 192 children evaluated for microcytosis at our tertiary center between 2007 and 2017 and diagnosed as heterozygotes for the -α3.7 deletion. Additional α-thalassemia mutations, iron deficiency anemia, and β-thalassemia were ruled out. Laboratory parameters were compared to age- and sex-matched reference values.

RESULTS

The -α3.7 carriers had significantly lower Hb and mean corpuscular volume (MCV) than the reference population, and significantly higher red blood cell counts across all age groups. The greatest reduction in Hb level appeared among male adolescents, while MCV was consistently 2 SDs lower than normal in most patients older than 2 years.

CONCLUSION

Heterozygosity for the -α3.7 deletion was associated with clinically significant microcytosis and mild anemia in our pediatric population. In the absence of iron deficiency and β-thalassemia, this finding provides a diagnosis for mild microcytic anemia, making additional investigations of microcytosis unnecessary.

Isoflurane and sodium nitroprusside reduce the depressant effects of protamine sulfate on isolated ischemic rat hearts

The administration of protamine sulfate (protamine) to reverse the action of heparin is associated with adverse reactions. We studied the effects of protamine and isoflurane on isolated, perfused rat hearts previously subjected to cardioplegic ischemia. Hearts were perfused with oxygenated Krebs-Henseleit (KH) solution for 30 min, then subjected to cardioplegic ischemia for 30 min (KCl 16 mEq/L at 31 degrees C) and 5 min reperfusion. Drug exposure lasted 15 min, and the recovery period was 60 min. Test groups were control, protamine (10 microg/mL), isoflurane (1.5%), protamine +/- isoflurane, sodium nitroprusside (SNP) (2.5 ng/mL), and SNP +/- protamine. Left ventricular developed pressure (LVP), coronary flow, and myocardial oxygen consumption were depressed by protamine to 30% +/- 4%, 47% +/- 4%, and 39% +/- 4% of baseline (P < 0.001 versus control), respectively. Isoflurane and SNP afforded partial protection from the effects of protamine: LVP was 57% +/- 5% and 51% +/- 3% of baseline, respectively (P < 0.05 versus protamine alone and control); coronary flow was 70% +/- 6% and 97% +/- 12% of baseline, respectively (P < 0.05 versus protamine alone; P < 0.05 for isoflurane versus control); and O2 consumption was 69% +/- 6% and 88% +/- 15% of baseline, respectively (P < 0.05 versus protamine; P < 0.05 for isoflurane versus control). In this model, protamine-induced myocardial depression and coronary vasoconstriction were less pronounced in the presence of either isoflurane or SNP.

IMPLICATIONS

We examined the interactions of isoflurane, sodium nitroprusside, and protamine in a rat heart model and found that both isoflurane and sodium nitroprusside partially protect the heart from the depressant effects of protamine. This finding is significant, as these drugs are often used in heart surgery.

The influence of aprotinin on myocardial function after liver ischemia-reperfusion

BACKGROUND

The beneficial effect of aprotinin, a naturally occurring protease inhibitor, on preservation of organs such as the liver, kidney and lung has been documented.

OBJECTIVE

To explore the effects of hepatic ischemia and reperfusion on both liver and myocardial function, using a dual isolated perfused organ model with and without aprotinin.

METHODS

Isolated rat livers were stabilized for 30 minutes with oxygenated modified Krebs-Henseleit solution at 37 degrees C. Livers were then perfused continuously with KH or KH + aprotinin 10(6) KIU/L for an additional 135 min. Livers of two other groups were made globally ischemic for 120 min, then perfused for 15 min with KH or with KH + aprotinin. Isolated hearts (Langendorff preparation) were stabilized for 30 min and then reperfused with KH or KH + aprotinin exiting the liver for 15 min. The liver's circuit was disconnected, and hearts were re-circulated with the accumulated liver + heart effluent for an additional 50 min.

RESULTS

In the ischemia and ischemia + aprotinin groups, portal vein pressure (1 and 15 min reperfusion) was 331 +/- 99% and 339 +/- 61% vs. 308 +/- 81% and 193 +/- 35% of baseline, respectively (P < 0.03 vs. ischemia). There were no other differences in the enzyme leakage between aprotinin-treated or untreated ischemic livers. Left ventricular pressure was stable in the controls. However, LV pressure in groups perfused with ischemic liver effluent declined within 65 min reperfusion, whether aprotinin treated or not (84 +/- 8% and 73 +/- 5% of baseline, respectively, P < 0.004 only for ischemia vs. control).

CONCLUSION

When aprotinin was used, LV pressure was inclined to be higher while liver portal vein pressure was lower, thus providing protection against liver and heart reperfusion injury.

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.

Genetic backgrounds and clinical characteristics of congenital neutropenias in Israel

BACKGROUND

Congenital neutropenias are characterized by severe infections and a high risk of myeloid transformation; the causative genes vary across ethnicities. The Israeli population is characterized by an ethnically diverse population with a high rate of consanguinity.

OBJECTIVE

To evaluate the clinical and genetic spectrum of congenital neutropenias in Israel.

METHODS

We included individuals with congenital neutropenias listed in the Israeli Inherited Bone Marrow Failure Registry. Sanger sequencing was performed for ELANE or G6PC3, and patients with wild-type ELANE/G6PC3 were referred for next-generation sequencing.

RESULTS

Sixty-five patients with neutropenia were included. Of 51 patients with severe congenital neutropenia, 34 were genetically diagnosed, most commonly with variants in ELANE (15 patients). Nine patients had biallelic variants in G6PC3, all of consanguineous Muslim Arab origin. Other genes involved were SRP54, JAGN1, TAZ, and SLC37A4. Seven patients had cyclic neutropenia, all with pathogenic variants in ELANE, and seven had Shwachman-Diamond syndrome caused by biallelic SBDS variants. Eight patients (12%) developed myeloid transformation, including six patients with an unknown underlying genetic cause. Nineteen (29%) patients underwent hematopoietic stem cell transplantation, mostly due to insufficient response to treatment with granulocyte-colony stimulating factor or due to myeloid transformation.

CONCLUSIONS

The genetic spectrum of congenital neutropenias in Israel is characterized by a high prevalence of G6PC3 variants and an absence of HAX1 mutations. Similar to other registries, for 26% of the patients, a molecular diagnosis was not achieved. However, myeloid transformation was common in this group, emphasizing the need for close follow-up.

A Variable Clinical Presentation of Hemoglobin City of Hope

Hemoglobin City of Hope (Hb-COH), NC_000011.9(NM_000518.5):c.208G > A; NP_000509.1:p.(Gly70Ser), has rarely been described. The presentation ranges from asymptomatic heterozygosity to significant anemia in patients carrying an additional pathogenic variant in β-globin. To elucidate the clinical spectrum of Hb-COH, we analyzed 31 individuals carrying the variant, including, for the first time, homozygous individuals. Seven patients who were compound heterozygous for Hb-COH and an additional variant in β-globin, presented with mild-to-severe microcytic anemia and elevated hemoglobin-A2. Three (43%) of these also had elevated fetal hemoglobin, but none required blood transfusions. Seven patients coinherited Hb-COH with an -α3.7-deletion (NG_000006.1:g.34247_38050del), their presentation ranged from mild microcytic anemia to normal blood counts. Three homozygous and 14 heterozygous individuals for Hb-COH had normal blood counts. Most Hb-COH alleles whose origin was traceable were from Ashkenazi Jews (70.4%). To conclude, while isolated Hb-COH appears asymptomatic even in the homozygous state, it may cause significant anemia when coinherited with an additional pathogenic variant in β-globin. Understanding the full impact of Hb-COH is crucial for optimal patient management and for genetic counseling.

Clinical and Laboratory Characteristics of Pediatric Patients With ACKR1/DARC-Associated Neutropenia

BACKGROUND

ACKR1/DARC-associated neutropenia (ADAN), resulting from homozygosity for a single nucleotide polymorphism (SNP) in the ACKR1/DARC gene (rs2814778), is a common cause of benign neutropenia that primarily affects individuals of African and Jewish Yemenite descent. We aimed to characterize ADAN in pediatric patients in Israel, given its ethnically diverse population.

PROCEDURE

We assessed children with isolated neutropenia treated during 2018-2023 at one pediatric center, for the ACKR1/DARC polymorphism, using Sanger sequencing or targeted next-generation sequencing.

RESULTS

Of 115 patients evaluated, 49 (42.6%) were diagnosed with ADAN; of these, 29 (59%) had absolute neutrophil counts in the severe range (0-0.5 × 109/L) at diagnosis. The allele distribution revealed 37% of Muslim Arab and 61% of Jewish origin. Yemenite, Ethiopian, Mediterranean, Asian, and European ancestry were included; 59% had a family history of neutropenia. The median age at the first neutropenia detection was 1.2 years; 91.8% were identified during routine blood counts. The median absolute neutrophil count at diagnosis was 0.5 × 109/L (interquartile range: 0.3). An increased susceptibility to infections was not found either before or during the median follow-up period of 2.5 years (interquartile range: 1.54) after the diagnosis of ADAN. In 34 patients (72.3%), neutrophil counts were in the normal range during febrile illnesses.

CONCLUSIONS

We identified ADAN in individuals of variable ethnicities, almost half with severe neutropenia. We recommend testing for ADAN in all children with isolated neutropenia without severe infections. Homozygosity for the ACKR1/DARC rs2814778 SNP may obviate the need for further investigation, follow-up, or treatment in specific clinical scenarios.

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

Biallelic 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.