Human C-terminal CUBN variants associate with chronic proteinuria and normal renal function.

BACKGROUNDProteinuria is considered an unfavorable clinical condition that accelerates renal and cardiovascular disease. However, it is not clear whether all forms of proteinuria are damaging. Mutations in CUBN cause Imerslund-Gräsbeck syndrome (IGS), which is characterized by intestinal malabsorption of vitamin B12 and in some cases proteinuria. CUBN encodes for cubilin, an intestinal and proximal tubular uptake receptor containing 27 CUB domains for ligand binding.METHODSWe used next-generation sequencing for renal disease genes to genotype cohorts of patients with suspected hereditary renal disease and chronic proteinuria. CUBN variants were analyzed using bioinformatics, structural modeling, and epidemiological methods.RESULTSWe identified 39 patients, in whom biallelic pathogenic variants in the CUBN gene were associated with chronic isolated proteinuria and early childhood onset. Since the proteinuria in these patients had a high proportion of albuminuria, glomerular diseases such as steroid-resistant nephrotic syndrome or Alport syndrome were often the primary clinical diagnosis, motivating renal biopsies and the use of proteinuria-lowering treatments. However, renal function was normal in all cases. By contrast, we did not found any biallelic CUBN variants in proteinuric patients with reduced renal function or focal segmental glomerulosclerosis. Unlike the more N-terminal IGS mutations, 37 of the 41 proteinuria-associated CUBN variants led to modifications or truncations after the vitamin B12-binding domain. Finally, we show that 4 C-terminal CUBN variants are associated with albuminuria and slightly increased GFR in meta-analyses of large population-based cohorts.CONCLUSIONCollectively, our data suggest an important role for the C-terminal half of cubilin in renal albumin reabsorption. Albuminuria due to reduced cubilin function could be an unexpectedly common benign condition in humans that may not require any proteinuria-lowering treatment or renal biopsy.FUNDINGATIP-Avenir program, Fondation Bettencourt-Schueller (Liliane Bettencourt Chair of Developmental Biology), Agence Nationale de la Recherche (ANR) Investissements d'avenir program (ANR-10-IAHU-01) and NEPHROFLY (ANR-14-ACHN-0013, to MS), Steno Collaborative Grant 2018 (NNF18OC0052457, to TSA and MS), Heisenberg Professorship of the German Research Foundation (KO 3598/5-1, to AK), Deutsche Forschungsgemeinschaft (DFG) Collaborative Research Centre (SFB) KIDGEM 1140 (project 246781735, to CB), and Federal Ministry of Education and Research (BMB) (01GM1515C, to CB).

Whole exome sequencing identifies a new mutation in the SLC19A2 gene leading to thiamine-responsive megaloblastic anemia in an Egyptian family.

BACKGROUND: The Solute Carrier Family 19 Member 2 (SLC19A2, OMIM *603941) encodes the thiamine transporter 1 (THTR-1) that brings thiamine (Vitamin B1) into cells. THTR-1 is the only thiamine transporter expressed in bone marrow, cochlear, and pancreatic beta cells. THTR-1 loss-of-function leads to the rare recessive genetic disease Thiamine-Responsive Megaloblastic Anemia (TRMA, OMIM #249270). METHODS: In vitro stimulated blood lymphocytes were used for cytogenetics and the isolation of genomic DNA used to perform whole exome sequencing (WES). To validate identified mutations, direct Sanger sequencing was performed following PCR amplification. RESULTS: A 6-year-old male born from a consanguineous couple presenting bone marrow failure and microcephaly was referred to our clinic for disease diagnosis. The patient presented a normal karyotype and no chromosomal fragility in response to DNA damage. WES analysis led to the identification of a new pathogenic variant in the SLC19A2 gene (c.596C>G, pSer199Ter) allowing to identify the young boy as a TRMA patient. CONCLUSION: Our analysis extend the number of inactivating mutations in SLC19A2 leading to TRMA that could guide future prenatal diagnosis for the family and follow-up for patients.

Loss-of-Function Mutation in Thiamine Transporter 1 in a Family With Autosomal Dominant Diabetes.

Solute Carrier Family 19 Member 2 (SLC19A2) encodes thiamine transporter 1 (THTR1), which facilitates thiamine transport across the cell membrane. SLC19A2 homozygous mutations have been described as a cause of thiamine-responsive megaloblastic anemia (TRMA), an autosomal recessive syndrome characterized by megaloblastic anemia, diabetes, and sensorineural deafness. Here we describe a loss-of-function SLC19A2 mutation (c.A1063C: p.Lys355Gln) in a family with early-onset diabetes and mild TRMA traits transmitted in an autosomal dominant fashion. We show that SLC19A2-deficient ß-cells are characterized by impaired thiamine uptake, which is not rescued by overexpression of the p.Lys355Gln mutant protein. We further demonstrate that SLC19A2 deficit causes impaired insulin secretion in conjunction with mitochondrial dysfunction, loss of protection against oxidative stress, and cell cycle arrest. These findings link SLC19A2 mutations to autosomal dominant diabetes and suggest a role of SLC19A2 in ß-cell function and survival.

A novel mutation in the SLC19A2 gene in a Turkish male with thiamine-responsive megaloblastic anemia syndrome.

Odaman-Al I, Gezdirici A, Yildiz M, Ersoy G, Aydogan G, Salcioglu Z, Tahtakesen TN, Önal H, Küçükemre-Aydin B. A novel mutation in the SLC19A2 gene in a Turkish male with thiamine-responsive megaloblastic anemia syndrome. Turk J Pediatr 2019; 61: 257-260. Thiamine-responsive megaloblastic anemia (TRMA) is a very rare syndrome characterized by the triad of early onset megaloblastic anemia, sensorineural deafness and diabetes mellitus. Here we report, a 5-year-old boy who presented with transfusion dependent anemia and diabetes mellitus and was diagnosed with TRMA. Besides reporting a novel mutation of the causative gene SLC19A2, we wanted to emphasize this syndrome in the aspect of coexistence of insulin dependent diabetes, transfusion dependent anemia and thrombocytopenia.

A novel mutation in the SLC19A2 gene in a Turkish male with thiamine-responsive megaloblastic anemia syndrome.

Odaman-Al I, Gezdirici A, Yildiz M, Ersoy G, Aydogan G, Salcioglu Z, Tahtakesen TN, Önal H, Küçükemre-Aydin B. A novel mutation in the SLC19A2 gene in a Turkish male with thiamine-responsive megaloblastic anemia syndrome. Turk J Pediatr 2019; 61: 257-260. Thiamine-responsive megaloblastic anemia (TRMA) is a very rare syndrome characterized by the triad of early onset megaloblastic anemia, sensorineural deafness and diabetes mellitus. Here we report, a 5-year-old boy who presented with transfusion dependent anemia and diabetes mellitus and was diagnosed with TRMA. Besides reporting a novel mutation of the causative gene SLC19A2, we wanted to emphasize this syndrome in the aspect of coexistence of insulin dependent diabetes, transfusion dependent anemia and thrombocytopenia.

Structural assembly of the megadalton-sized receptor for intestinal vitamin B12 uptake and kidney protein reabsorption.

The endocytic receptor cubam formed by the 460-kDa protein cubilin and the 45-kDa transmembrane protein amnionless (AMN), is essential for intestinal vitamin B12 (B12) uptake and for protein (e.g. albumin) reabsorption from the kidney filtrate. Loss of function of any of the two components ultimately leads to serious B12 deficiency and urinary protein loss in humans (Imerslund-Gräsbeck's syndrome, IGS). Here, we present the crystal structure of AMN in complex with the amino-terminal region of cubilin, revealing a sophisticated assembly of three cubilin subunits combining into a single intertwined ß-helix domain that docks to a corresponding three-faced ß-helix domain in AMN. This ß-helix-ß-helix association thereby anchors three ligand-binding cubilin subunits to the transmembrane AMN. Electron microscopy of full-length cubam reveals a 700-800 Å long tree-like structure with the potential of dimerization into an even larger complex. Furthermore, effects of known human mutations causing IGS are explained by the structural information.

A Novel Mutation of SLC19A2 in a Chinese Zhuang Ethnic Family with Thiamine-Responsive Megaloblastic Anemia.

BACKGROUND/AIMS: Thiamine-responsive megaloblastic anemia syndrome is a rare autosomal recessive disorder resulting from mutations in SLC19A2, and is mainly characterized by megaloblastic anemia, diabetes, and progressive sensorineural hearing loss. METHODS: We study a Chinese Zhuang ethnicity family with thiamine-responsive megaloblastic anemia. The proband of the study presented with anemia and diabetes, similar to his late brother, as well as visual impairment. All clinical manifestations were corrected with thiamine (30 mg/d) supplementation for 1-3 months, except for visual impairment, which was irreversible. The presence of mutations in all exons and the flanking sequences of the SLC19A2 gene were analyzed in this family based on the proband's and his brother's clinical data. Computer analysis and prediction of the protein conformation of mutant THTR-1. The relative concentration of thiamine pyrophosphate in the proband's whole blood before and after initiation of thiamine supplement was measured by high performance liquid chromatography (HPLC). RESULTS: Gene sequencing showed a homozygous mutation in exon 6 of the SLC19A2 gene (c.1409insT) in the proband. His parents and sister were diagnosed as heterozygous carriers of the c.1409insT mutation. Computer simulation showed that the mutations caused a change in protein conformation. HPLC results suggested that the relative concentration of thiamine pyrophosphate in the proband's whole blood after thiamine supplement was significantly different (P=0.016) from that at baseline. CONCLUSIONS: This novel homozygous mutation (c.1409insT) caused the onset of thiamine-responsive megaloblastic anemia in the proband.

Folate deficiency increases chromosomal damage and mutations in hematopoietic cells in the transgenic mutamouse model.

Folate deficiency causes megaloblastic anemia and neural tube defects, and is also associated with some cancers. In vitro, folate deficiency increases mutation frequency and genome instability, as well as exacerbates the mutagenic potential of known environmental mutagens. Conversely, it remains unclear whether or not elevated folic acid (FA) intakes are beneficial or detrimental to the induction of DNA mutations and by proxy human health. We used the MutaMouse transgenic model to examine the in vivo effects of FA deficient, control, and supplemented diets on somatic DNA mutant frequency (MF) and genome instability in hematopoietic cells. We also examined the interaction between FA intake and exposure to the known mutagen N-ethyl-N-nitrosourea (ENU) on MF. Male mice were fed the experimental diets for 20 weeks from weaning. Half of the mice from each diet group were gavaged with 50 mg/kg body weight ENU after 10 weeks on diet and remained on their respective diet for an additional 10 weeks. Mice fed a FA-deficient diet had a 1.3-fold increase in normochromatic erythrocyte micronucleus (MN) frequency (P = 0.034), and a doubling of bone marrow lacZ MF (P = 0.035), compared to control-fed mice. Mice exposed to ENU showed significantly higher bone marrow lacZ and Pig-a MF, but there was no effect of FA intake on ENU-induced MF. These data indicate that FA deficiency increases mutations and MN formation in highly proliferative somatic cells, but that FA intake does not mitigate ENU-induced mutations. Also, FA intake above adequacy had no beneficial or detrimental effect on mutations or MN formation. Environ. Mol. Mutagen. 59:366-374, 2018. © 2018 Her Majesty the Queen in Right of Canada 2018.

[Defect of thiamine transport and activation and related disease].

Thiamine, also known as vitamin B1, is an important vitamin for the body. The activated form of thiamine pyrophosphate is involved in cell metabolism as an important co-enzyme. Defects of thiamine transport and activation may cause lack of thiamine and affection of cell metabolism, leading a variety of diseases. This review has summarized defects of thiamine transport and activation and related diseases.

Unmethylated promoter DNA correlates with p53 expression and apoptotic levels only in Vitamin B9 and B12 deficient megaloblastic anemia but not in non-megaloblastic anemia controls.

Cyanocobalamin (Vitamin B12, VB12) and Folic acid (Vitamin B9, VB9) deficiency leads to anemia in women. We have recently shown low VB12 and VB9 levels in the serum of megaloblastic anemia (MBA) patients. Further, our study demonstrated elevated homocysteine and p53, respectively, in the serum and bone marrow aspirates of MBA patients but not in non-MBA subjects. However, it is unknown whether any gender specific variation in VB12 and VB9 level exists in MBA and non-MBA patients? In addition, it is unclear whether low VB12 and VB9 has a role in the regulation of p53 expression in MBA patients? And whether elevated p53 is functionally active? If so, does bone marrow aspirates of MBA patients show elevated apoptosis. Hence, we have analyzed VB12 and VB9 levels in MBA patients and compared with non-MBA subjects. Next, methylation status of p53 promoter was determined and correlated with p53 expression. Furthermore, the level of apoptosis in bone marrow aspirate paraffin blocks was estimated using TUNEL staining. In conclusion, low VB12 and VB9 in male and female patients directly correlate with p53 promoter unmethylation status, but, inversely correlate with p53 protein expression and its activity, only in MBA cases but not in non-MBA controls.

Vitamin B12 deficiency from the perspective of a practicing hematologist.

B12 deficiency is the leading cause of megaloblastic anemia, and although more common in the elderly, can occur at any age. Clinical disease caused by B12 deficiency usually connotes severe deficiency, resulting from a failure of the gastric or ileal phase of physiological B12 absorption, best exemplified by the autoimmune disease pernicious anemia. There are many other causes of B12 deficiency, which range from severe to mild. Mild deficiency usually results from failure to render food B12 bioavailable or from dietary inadequacy. Although rarely resulting in megaloblastic anemia, mild deficiency may be associated with neurocognitive and other consequences. B12 deficiency is best diagnosed using a combination of tests because none alone is completely reliable. The features of B12 deficiency are variable and may be atypical. Timely diagnosis is important, and treatment is gratifying. Failure to diagnose B12 deficiency can have dire consequences, usually neurological. This review is written from the perspective of a practicing hematologist.

Mild orotic aciduria in UMPS heterozygotes: a metabolic finding without clinical consequences.

BACKGROUND: Elevated urinary excretion of orotic acid is associated with treatable disorders of the urea cycle and pyrimidine metabolism. Establishing the correct and timely diagnosis in a patient with orotic aciduria is key to effective treatment. Uridine monophosphate synthase is involved in de novo pyrimidine synthesis. Uridine monophosphate synthase deficiency (or hereditary orotic aciduria), due to biallelic mutations in UMPS, is a rare condition presenting with megaloblastic anemia in the first months of life. If not treated with the pyrimidine precursor uridine, neutropenia, failure to thrive, growth retardation, developmental delay, and intellectual disability may ensue. METHODS AND RESULTS: We identified mild and isolated orotic aciduria in 11 unrelated individuals with diverse clinical signs and symptoms, the most common denominator being intellectual disability/developmental delay. Of note, none had blood count abnormalities, relevant hyperammonemia or altered plasma amino acid profile. All individuals were found to have heterozygous alterations in UMPS. Four of these variants were predicted to be null alleles with complete loss of function. The remaining variants were missense changes and predicted to be damaging to the normal encoded protein. Interestingly, family screening revealed heterozygous UMPS variants in combination with mild orotic aciduria in 19 clinically asymptomatic family members. CONCLUSIONS: We therefore conclude that heterozygous UMPS-mutations can lead to mild and isolated orotic aciduria without clinical consequence. Partial UMPS-deficiency should be included in the differential diagnosis of mild orotic aciduria. The discovery of heterozygotes manifesting clinical symptoms such as hypotonia and developmental delay are likely due to ascertainment bias.

Beta cell function and clinical course in three siblings with thiamine-responsive megaloblastic anemia (TRMA) treated with thiamine supplementation.

Three siblings with thiamine-responsive megaloblastic anemia (TRMA) with a homozygous c.454delGGCATinsAT mutation in SLC19A2 are described. The index case presented at 14 months' old with severe non-ketotic hyperglycemia, dehydration, seizures and sinovenous thrombosis. She was started on insulin and developed sensorineural hearing loss around 2 years old. Two siblings were found to have the same mutation and were started on thiamine. One sibling developed transient hyperglycemia after several years of thiamine supplementation of 12 mg/kg that resolved with an increased thiamine dose (23 mg/kg). A younger sibling continues to remain diabetes-free on thiamine (24 mg/kg). The clinical course in this family suggests that there is an effect of thiamine on pancreatic beta cell function in patients with TRMA given the resolution of impaired fasting glucose with increasing thiamine dose in one sibling and the lack of diabetes to date in the siblings that were treated early with thiamine.

Comparative Assessment of Vitamin-B12, Folic Acid and Homocysteine Levels in Relation to p53 Expression in Megaloblastic Anemia.

BACKGROUND: Megaloblastic anemia (MBA), also known as macrocytic anemia, is a type of anemia characterized by decreased number of RBCs as well as the presence of unusually large, abnormal and poorly developed erythrocytes (megaloblasts), which fail to enter blood circulation due to their larger size. Lack of vitamin-B12 (VB12) and / or folate (Vitamin-B9, VB9) with elevated homocysteine is the key factor responsible for megaloblastic anemia. Prior studies have demonstrated the induction of apoptosis in these abnormal under-developed erythrocytes. However, it is not clear whether this apoptosis induction is due to elevated p53 level or due to any other mechanism. Furthermore, it is also not fully known whether decreased vitamin-B12 and / or folate are responsible for apoptosis induction mediated by p53 in pre-erythroblasts. METHODS: Levels of serum VB9, VB12 and homocysteine in 50 patients suffering from MBA were compared with 50 non-megaloblastic anemia control subjects, who were referred by the clinicians for bone marrow examination for medical conditions other than MBA. Next, we have measured the p53 expression in the paraffin embedded blocks prepared from bone marrow biopsy, using immunohistochemistry, and the expression levels correlated with VB9 and VB12 levels. RESULTS: Out of 50 MBA patients 40 (80%) and 44 (88%) subjects had very low VB12 and VB9 levels respectively. In contrast, only 2 (4%) and 12 (24%) non-megaloblastic anemia controls, out of 50 subjects, had low VB12 and VB9 respectively. Correlating with low vitamin B9 and B12, the homocysteine levels were high in 80% cases. But, only 20% non-megaloblastic controls exhibited high homocysteine in plasma. Immunohistochemical analysis for p53 expression showed a significantly high level of expression in MBA cases and no-or very low-expression in control subjects. Our correlation studies comparing the VB12 and VB9 levels with p53 expression concludes unusually high p53 levels in patients suffering from VB12 and VB9 deficiency induced MBA compared to control subjects not suffering from MBA. CONCLUSION: Tumor protein p53 is the key protein expressed heavily in the bone marrow biopsies of patients suffering from VB12 and VB9 deficiency induced MBA but not in control subjects. Hence, p53 expression could be used as a surrogate marker for confirming the VB9 and VB12 induced MBA.

Lessons in biology from patients with inherited disorders of vitamin B12 and folate metabolism.

BACKGROUND: Over the last forty years, our laboratory has accumulated a collection of over 1000 cultured fibroblast lines derived from patients from around the world referred with signs of inborn errors of cobalamin or folate metabolism, including several hundred with complementation-confirmed diagnoses. By accurately classifying patient disorders into classes representing blocks affecting specific reactions, we have provide the basis for rational assessment of phenotypic heterogeneity, and development of methods for diagnosis, treatment and prognosis. These resources have been valuable in identification of causal genes for known inborn errors. Since 2000, we and our collaborators identified the genes for the cblA (MMAA), cblB (MMAB), cblC (MMACHC), cblD (MMADHC), and cblF (LMBRD1) disorders. RESULTS: Whole exome sequencing of DNA from a patient with severe combined immunodeficiency (SCID), megaloblastic anemia and hemolytic uremic syndrome identified mutations in the MTHFD1 gene, which encodes a trifunctional enzyme involved in interconversion of folate coenzyme derivatives. This disorder demonstrates the importance de novo pyrimidine synthesis in the etiology of SCID. Mutations in the ABCD4 gene have been identified in four patients with accumulation of unbound cobalamin in lysosomes; this gene encodes a lysosomal membrane protein that plays a role in the transport of cobalamin across this membrane. Mutations in the HCFC1 gene on the X chromosome have been identified in several male patients that had received a diagnosis of cblC on the basis of complementation studies in cultured fibroblasts. HCFC1 encodes a transcription factor that regulates expression of a number of genes, including MMACHC, the gene that is mutated in patients with the cblC disorder. These studies demonstrate that with the advent of affordable whole exome sequencing, it has been possible to identify genes for novel inborn errors of cobalamin metabolism, often working from a small number of affected patients.

Hereditary orotic aciduria with epilepsy and without megaloblastic anemia.

Hereditary orotic aciduria is a rare metabolic disease that results from a defect of uridine-5-monophosphate synthase (UMPS). In affected patients, main clinical symptoms are a markedly increased urinary excretion of orotic acid combined with megaloblastic anemia. This report describes a new case of UMPS deficiency without megaloblastic anemia but with epilepsy.

Human mutations in methylenetetrahydrofolate dehydrogenase 1 impair nuclear de novo thymidylate biosynthesis.

An inborn error of metabolism associated with mutations in the human methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) gene has been identified. The proband presented with SCID, megaloblastic anemia, and neurologic abnormalities, but the causal metabolic impairment is unknown. SCID has been associated with impaired purine nucleotide metabolism, whereas megaloblastic anemia has been associated with impaired de novo thymidylate (dTMP) biosynthesis. MTHFD1 functions to condense formate with tetrahydrofolate and serves as the primary entry point of single carbons into folate-dependent one-carbon metabolism in the cytosol. In this study, we examined the impact of MTHFD1 loss of function on folate-dependent purine, dTMP, and methionine biosynthesis in fibroblasts from the proband with MTHFD1 deficiency. The flux of formate incorporation into methionine and dTMP was decreased by 90% and 50%, respectively, whereas formate flux through de novo purine biosynthesis was unaffected. Patient fibroblasts exhibited enriched MTHFD1 in the nucleus, elevated uracil in DNA, lower rates of de novo dTMP synthesis, and increased salvage pathway dTMP biosynthesis relative to control fibroblasts. These results provide evidence that impaired nuclear de novo dTMP biosynthesis can lead to both megaloblastic anemia and SCID in MTHFD1 deficiency.

Thiamine-responsive megaloblastic anemia syndrome with Ebstein anomaly: a case report.

UNLABELLED: Thiamine-responsive megaloblastic anemia (TRMA) or Roger syndrome is a rare autosomal recessive disorder characterized by the occurrence of multiple clinical manifestations including megaloblastic anemia, diabetes mellitus, and sensorineural deafness. A few patients have been also described with congenital cardiac malformations. The patients usually respond to treatment with pharmacological doses of thiamine. Mutations in the SLC19A2 gene, located at chromosome 1q24.2, are responsible for this syndrome. Here, we present two new Iranian TRMA patients who were homozygous for c.697C > T mutation in the SLC19A2 gene. On follow-up, one of the patients showed Ebstein anomaly. CONCLUSION: The present study confirms the variability of the clinical manifestations caused by the same mutation within patients with TRMA syndrome. Therefore, follow-up of the affected children should be considered.

[Expression characteristics of differentiation antigens on granulocytes in patients with megaloblastic anemia].

This study was aimed to explore the change characteristics of cell differentiation antigen (CD) on bone marrow (BM) granulocytes in patients,with megaloblastic anemia (MA). In combination with BM cell morphology, hemogram, level of blood serum folic acid, level of Vit B(12), cell genetics and biological examination data, the BM granulocytes differentiation antigens in 13 patients with MA were detected by flow cyto metry and analyzed retrospectively, in order to summarize the variation characteristics of CD13, CD33 and CD15 expressed on myeloid cells in patient with MA, including forward scatter light (FSC) and side scatter light (SSC) signal intensity, then these findings were compared with that in normal healthy persons. The results showed that the expression rates of CD13, CD15 and CD33 on granulocytic in patients with MA and normal healthy persons were (44.53 ± 16)%, (96.16 ± 2.67)%, (80.81 ± 14.71)% and (62.33 ± 11.02)%, (99.53 ± 0.46)%, (70.00 ± 7.81)% respectively, in which the expression rate of CD13 and CD15 in patients with MA decreased (P < 0.01), while the expression rate of CD33 increased (P < 0.01). The mean fluorescence intensity (MFI) of CD13, CD15, CD33, SSC and FSC in MA patients and normal healthy persons were 3.39 ± 1.41, 14.29 ± 6.59, 1.95 ± 0.94, 478.78 ± 70.43, 633.46 ± 75.53 and 5.12 ± 1.15, 20.67 ± 5.13, 1.04 ± 0.17, 332.00 ± 38.16, 537.00 ± 16.70 respectively, in which the MFI of CD13 and CD15 on granulocytes in MA patients decreased (P < 0.01),while the MFI of FSC,SSC and CD33 increased (P < 0.01 and P < 0.05). It is concluded that not only the morphology of BM granulocytes in patents with MA shows dysmaturity, but the expressing feature of differentiation antigens on BM granulocytes in MA patients also displays dysmaturity.These findings will contribute to the clinical diagnosis of MA patients.