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).

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.

Clinicohematological Study of Pancytopenia in a Tertiary Care Hospital of Western Region of Nepal

INTRODUCTION

Pancytopenia is a relatively common hematological entity and is a manifestation of many illnesses which can be life threatening at times. The severity of pancytopenia and the underlying pathology determine the management and prognosis. This study was conducted to evaluate hematological and bone marrow findings in patients presenting with pancytopenia.

METHODS

A prospective observational study was conducted in Department of Pathology, Manipal College of Medical Sciences, Pokhara from January 2011 to December 2016. Clinical and hematological parameters including bone marrow aspiration and biopsy were evaluated in all patients who presented with pancytopenia.

RESULTS

Among 138 cases studied, patients' age ranged from 2 to 82 years with a mean age of 43.95 years, and there was male predominance. Most of the patients presented with generalized weakness, pallor, dypnoea and fever. Hypoplastic marrow was seen in 38 (27.5%) cases, followed by 26 (18.8%) cases of megaloblastic anemia and 19 (13.76%) cases of acute leukemia. Other findings included one case each of hemophagocyosis, leishmaniasis, plasmodium vivex malaria and metastatic carcinoma.

CONCLUSIONS

This study highlights that pancytopenia is a common hematological problem and that the study of detailed primary hematological investigations along with bone marrow study in patients with pancytopenia will help to identify the cause for further planning and management.

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.

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.

[Clinically relevant possibilities and limits of differential diagnosis of megaloblastic anemia and myelodysplastic syndrome - refractory anemia type in bone marrow biopsies]

INTRODUCTION

Megaloblastic anemia (MA) represents a subtype of macrocytic anemia caused by impaired DNA synthesis, mostly due to folate and vitamin B12 deficiency. Its mildest forms lead to macrocytosis without concomitant anemia, but more severe forms to thrombocytopenia and/or leucopenia as well. In majority of the cases, the diagnosis of MA dose not represent a serious clinical problem, however, other causes of macrocytosis including myelodysplastic syndrome (MDS) must be excluded.

MATERIAL AND METHODS

In the period 2004-2015 we identified in our registry 126 consecutive bone marrow (BM) biopsies of patients with cytopenia/s in peripheral blood and suspicion either on MA or MDS of refractory anemia (RA) type. We performed a retrospective analysis of BM biopsies focused on evaluation of parameters useful for the differential diagnosis, as represented by (a) cellularity and proportions of BM precursors, (b) and their topography, (c) presence of maturation defects and dysplastic changes, (d) grade and extent of myelofibrosis, (e) iron deposits and (f) presence of "inflammatory" response in BM. Histological analyses were supported by immunohistochemical examinations.

RESULTS

The series consisted of biopsies of 126 patients (61 men and 65 women) with average age 63 (14-88 years) - almost all patients (121/126) presented with anemia. Based on the findings we distinguished three diagnostic groups - MA (31 patients), MDS-RA (39) and bioptically unclasifiable case ("DIF DG" - 56 patients). Abnormalities of the BM cellularity were observed in 81 % and of topography in 73 % of all cases respectively. Megalobastic differentiation of erythropoesis was detected in 79 % and diagnostic dysplastic changes in 25 % of all biopsy cases. In 29 % of all biopsies ring sideroblasts were present, megakaryocytic nuclear lobulisation defects density changes were found in 61 % of all patients. In 14 % of all biopsies the BM myelofibrosis was absent, in contrast 5 % of the biopsies showed severe diffuse fibrosis. "Inflammatory" response was developed in 44 % of all biopsies. Iron deposits were absent in 26 %, decreased in 35 % and increased in 33 % of all the cases.

CONCLUSIONS

From the point of view of histopathologist it seems to be difficult to distinguish BM hematopoietic changes in patients with MA and MDS-RA respectivelly, as histological examinations allowed determination of a definitive and correct diagnosis in about 55% of the cases. The crucial problem represents a decision whether the observed changes really result from the development of a clonal disease.Key words: megaloblastic anemia - megaloblastic differentiation - refractory anemia.

Characterization and review of MTHFD1 deficiency: four new patients, cellular delineation and response to folic and folinic acid treatment

In the folate cycle MTHFD1, encoded by MTHFD1, is a trifunctional enzyme containing 5,10-methylenetetrahydrofolate dehydrogenase, 5,10-methenyltetrahydrofolate cyclohydrolase and 10-formyltetrahydrofolate synthetase activity. To date, only one patient with MTHFD1 deficiency, presenting with hyperhomocysteinemia, megaloblastic anaemia, hemolytic uremic syndrome (HUS) and severe combined immunodeficiency, has been identified (Watkins et al J Med Genet 48:590-2, 2011). We now describe four additional patients from two different families. The second patient presented with hyperhomocysteinemia, megaloblastic anaemia, HUS, microangiopathy and retinopathy; all except the retinopathy resolved after treatment with hydroxocobalamin, betaine and folinic acid. The third patient developed megaloblastic anaemia, infection, autoimmune disease and moderate liver fibrosis but not hyperhomocysteinemia, and was successfully treated with a regime that included and was eventually reduced to folic acid. The other two, elder siblings of the third patient, died at 9 weeks of age with megaloblastic anaemia, infection and severe acidosis and had MTFHD1 deficiency diagnosed retrospectively. We identified a missense mutation (c.806C > T, p.Thr296Ile) and a splice site mutation (c.1674G > A) leading to exon skipping in the second patient, while the other three harboured a missense mutation (c.146C > T, p.Ser49Phe) and a premature stop mutation (c.673G > T, p.Glu225*), all of which were novel. Patient fibroblast studies revealed severely reduced methionine formation from [(14)C]-formate, which did not increase in cobalamin supplemented culture medium but was responsive to folic and folinic acid. These additional cases increase the clinical spectrum of this intriguing defect, provide in vitro evidence of disturbed methionine synthesis and substantiate the effectiveness of folic or folinic acid treatment.

Dysplasia features of myelodysplastic syndrome in ethnically Chinese people

OBJECTIVE

It was our aim to study the diagnostic significances of various dysplasia characteristics in myelodysplastic syndrome (MDS).

METHODS

We analyzed 160 cases of primary MDS and a control group including 28 cases of paroxysmal nocturnal hemoglobinuria (PNH), 104 cases of idiopathic thrombocytopenic purpura (ITP), 53 cases of non-severe aplastic anemia (NSAA), 40 cases of megaloblastic anemia and 50 cases of infectious and autoimmune diseases. Peripheral blood smears and bone marrow morphology were reviewed.

RESULTS

There was no significant difference in the occurrence rates of a variety of dysplasias in three lineages among MDS, megaloblastic anemia and PNH; however, changes in qualities and quantities in three lineages between NSAA and MDS were significantly different. ITP and MDS showed statistical differences in multiple changes in myeloid and erythroid cells. Significant differences also existed in multiple changes in erythroid series and megakaryocytes between infectious and autoimmune diseases and MDS. Morphological abnormalities highly related with MDS included multinucleated erythroblasts, ringed sideroblasts, poikilocytosis and gigantocytes, pseudo-Pelger neutrophils, ring-shaped nucleus, and micromegakaryocytes.

CONCLUSIONS

It is difficult to discriminate megaloblastic anemia and PNH from MDS by means of cell morphology. Different dysplasias of MDS have specific diagnostic values.

The role of bone marrow aspirate and trephine samples in haematological diagnoses in patients referred to a teaching hospital in Ghana

INTRODUCTION AND METHODS

A bone marrow examination had been requested by the referring clinician in over half of the 250 patients referred to the haematology clinic at Konfo Anokye Teaching Hospital (KATH) between 1988 and 1998 for investigations for various haematological disorders. Although a full blood count and a peripheral blood film can go a long way to resolve some of these diagnostic challenges faced by doctors in the districts, this information was generally not provided in the referral letter. After careful selection, 80 patients actually underwent a bone marrow examination. The result of the full blood count and peripheral film were available before bone marrow sampling was done.

RESULTS

Lymphoproliferative disorders were the most common diseases that caused infiltration of the bone marrow. 27.5% of lymphomas were diagnosed on morphological examination of the bone marrow as high grade B cell NHL, 13.75% had tropical splenic lymphoma, 10% had chronic lymphocytic leukaemia (CLL) and 5% had disseminated high grade T cell lymphoma and 2.5% had Adult T cell Leukaemia Lymphoma (ATLL). Other disorders diagnosed after bone marrow examination include myelodysplastic syndrome (MDS), aplastic anaemia, megaloblastic anaemia and myelofibrosis. Only 8.75% of these patients had a normal bone marrow.

CONCLUSIONS

This study has demonstrated the complexity of using bone marrow examination in clinical diagnosis and emphasizes the need for referring clinicians to consider involving specialist input in difficult haematological cases before requesting bone marrow examination for their patients.

Identification and characterization of an inborn error of metabolism caused by dihydrofolate reductase deficiency

Dihydrofolate reductase (DHFR) is a critical enzyme in folate metabolism and an important target of antineoplastic, antimicrobial, and antiinflammatory drugs. We describe three individuals from two families with a recessive inborn error of metabolism, characterized by megaloblastic anemia and/or pancytopenia, severe cerebral folate deficiency, and cerebral tetrahydrobiopterin deficiency due to a germline missense mutation in DHFR, resulting in profound enzyme deficiency. We show that cerebral folate levels, anemia, and pancytopenia of DHFR deficiency can be corrected by treatment with folinic acid. The characterization of this disorder provides evidence for the link between DHFR and metabolism of cerebral tetrahydrobiopterin, which is required for the formation of dopamine, serotonin, and norepinephrine and for the hydroxylation of aromatic amino acids. Moreover, this relationship provides insight into the role of folates in neurological conditions, including depression, Alzheimer disease, and Parkinson disease.

[Ultrastructure of coronary microvessels in conditions of heart reperfusion following prolonged ischemia while applying various methods of artificial hypothermia]

It has been found out that in children with Roger's disease corrected in the conditions of two fundamentally different procedures of anesthetic management, myocardial reperfusion after cardiac arrest under artificial hypothermic circulation is accompanied by obstruction of more than 30% of coronary bed microvessels with hydropic endothelial cells or their cystiform fragments. The content of necrotic cells increases, while the "working" cells demonstrate a decrease in myocropinocytotic transport characteristics. Circulatory arrest under perfusionless hypothermia and immersion reperfusion do not result in a dramatic change of general morphology of microvessels as compared to the control group, while a heterogenic response of the structures responsible for transendothelial transfer of macromolecules provides the basis for recovery of the endothelium structure and function, as a patient's temperature reaches a standard value.

Bone marrow examination in cases of pancytopenia

This study was carried to identify the causes of pancytopenia and to find out the bone marrow morphology in cases of pancytopenia. It was a cross sectional study conducted over a period of two years in the Department of Pathology, Tribhuvan University Teaching Hospital. Bone marrow aspiration smears of patients fulfilling the criteria of pancytopenia were examined. The data obtained were analyzed using measures of central tendency. One hundred and forty eight cases underwent bone marrow aspiration and it constituted 15.74% of total cases. Mean age was 30 years (range, 1-79 years). 42 cases were children (28.37%). Male: female ratio was 1.5:1. The commonest cause was hypoplastic bone marrow seen in 43 cases (29%) followed by megaloblastic anemia in 35 cases (23.64%), and hematological malignancy in 32 cases (21.62%). Erythroid hyperplasia was seen in 29 cases (19.6%) and normal bone marrow was seen in 5 cases (3.38%). There was one case each of Niemann-Pick disease and metastatic neuroblastoma in children and chronic pure red cell aplasia and leishmaniasis in adults. Acute leukemia was the commonest hematological malignancy. In children, commonest finding was hypoplastic bone marrow (38.1%) while in adults megaloblastic anemia (30.18%) was commonest finding followed by hypoplastic anemia (25.47%). In present study bone marrow examination was able to establish diagnosis in 77% of cases. Hypoplastic marrow was the commonest diagnosis, followed by megaloblastic anemia, and hematological malignancies.

Incidence of megaloblastic anaemia and its correction in leishmaniasis--a prospective study at BPKIHS hospital, Nepal

Fifty (50) cases of Leishmaniasis were included in a prospective study after making the diagnosis based on the demonstration of L D Bodies on bone marrow aspirate. Hemoglobin (Hb) and total leucocyte count (TLC) were less than 10 gm/dl and 4000 per/ml respectively in 22 out of 50 cases. Among 50 cases, 30 showed macrocytic red cell and hypersegmented neutrophils on peripheral blood smear as features of megaloblastic anemia. Out of 30 cases of leishmaniasis with megaloblastic anemia, 10 cases showed decreased reticulocyte count. Bone marrow aspiration cytology showed megaloblastic maturation in erythroid series and giant metamyelocytes in myeloid series in all 30 cases of leishmaniasis with megaloblastic changes. Bone marrow iron was also increased in these cases. However megakaryocyte was normal in all. Among 30 cases of leishmaniasis with megaloblastic changes, 15 cases were treated with sodium antimony gluconate (SAG) only and other 15 with SAG, folic acid and Vit. B12. Rest 20 cases of leishmaniasis without megaloblastic changes were also treated with SAG only. After treatment with SAG alone as well as with SAG, folic acid and vit. B12, hemoglobin and TLC improved in all 50 cases. Of 15 cases of leishmaniasis with megaloblastic changes, who were treated with SAG, folic acid and vit. B12, the reticulocyte count reached at peak on the 7th day and normalized at the end of 4th week. Red blood cells (RBC) also became normocytic normochromic and neutrophils became normal on peripheral blood smear. But no change was observed in reticulocyte count, RBC and white blood cell (WBC) morphology on peripheral blood smear in cases of leishmaniasis without megaloblastic changes and other 15 cases of leishmaniasis with megaloblastic changes, who received SAG only.

Dorsal sural nerve conduction study in vitamin B12 deficiency with megaloblastic anemia

Peripheral neuropathy is frequently observed in B(12) deficiency. In spite of this, there is little knowledge about peripheral neuropathy in B(12) deficiency because the severity of clinical involvement of the central nervous system clearly outweighs signs and symptoms due to peripheral nervous system involvement. We primarily investigated peripheral neuropathy with dorsal sural conduction study, which is a new method for detection of early peripheral neuropathy, in B(12) deficiency with megaloblastic anemia. Conventional nerve conduction studies and tibial sensory-evoked potential (SEP) recording were also performed. Twenty-eight B(12)-deficient patients (15 male, 13 female, mean age 65.8 years) with megaloblastic anemia and 18 age- and sex-matched controls were included in the study. Although dorsal sural sensory nerve action potentials (SNAPs) were not recorded in 15 (54%) of 28 patients, only 9 (32%) of them were found to have polyneuropathy by conventional conduction studies. Furthermore, patients with dorsal sural SNAP had mean lower amplitude, mean longer latency, and slower velocity response when compared with controls. Twenty patients (71%) were diagnosed as having myelopathy by the combination of tibial SEP and neurological findings. Two patients whose dorsal sural SNAPs were not recorded had normal tibial SEP responses; therefore, these patients were considered to have isolated peripheral neuropathy. As a result, we conclude that dorsal sural nerve conduction study is a reliable method for detection of early peripheral neuropathy in B(12) deficiency.

[Ocular findings in megaloblastic anemia associated with diabetes. A case report]

Ocular involvements of Biermer's anaemia are rarely reported in literature. We present a case of Biermer's anaemia associated with diabetes. Ocular examination showed important conjinctival paleness, diffuse retinal ischemia, Roth's tasks, macular oedema and ischemic optic neuropathy. The patient was treated with vitamin B12 intramusculary. A month later, on examination, we noted a regression of optic neuropathy, the aggravation of ischemic retinopathy and persistence of macular oedema. The patient was treated with laser photocoagulation. The majority of ocular manifestations are reversible if treatment is underlaken early. The combination of diabetes with Biermer's anemia deteriorates the ischemic retinopathy and aggavates its prognosis.

MRI evaluation of cranial bone marrow signal intensity and thickness in chronic anemia

BACKGROUND AND PURPOSE

The aim is to assess the magnetic resonance imaging (MRI) findings for cranial bone marrow (CBM) signal intensity and thickness in patients with chronic anemia and compared these with findings in healthy subjects. We also investigated the relationships between CBM changes and age, type of anemia (hemolytic versus non-hemolytic), and severity of anemia.

METHODS

We quantitatively evaluated CBM signal intensity and thickness on images from 40 patients with chronic anemia (20 with congenital hemolytic anemia (HA) and 20 with acquired anemia) and compared these to findings in 28 healthy subjects. The intensity of CBM relative to scalp, white matter (WM), gray matter (GM), and muscle intensity was also investigated in patients and subjects in the control group. The sensitivity and specificity of CBM hypointense to GM and CBM hypointense to WM as markers of anemia were evaluated. Relationships between age and CBM thickness/intensity, and between anemia severity (hemoglobin (Hb) level) and CBM thickness/intensity were evaluated.

RESULTS

Cranial bone marrow signal intensity was lower in the chronic anemia patients than in the controls (P<0.001). In the control group, CBM intensity was higher than GM intensity, whereas the opposite was true in the patient group. The finding of CBM hypointense to GM was 85% sensitive and 67% specific as a marker of anemia. The corresponding statistics for CBM hypointense to WM were 90 and 46%. The patients had thicker CBM than the controls (temporal, P<0.05; parietal, P<0.005). The subgroup with hemolytic anemia had thicker parietal CBM than the subgroup with non-hemolytic anemia (NHA) (P<0.05) and exhibited thicker temporal and parietal CBM than the controls (temporal, P<0.05; parietal, P<0.001). The CBM thicknesses in the non-hemolytic anemia subgroup were similar to control values (P>0.05 for both). There were no correlations between age and CBM intensity or thickness, or between anemia severity and CBM intensity or thickness.

CONCLUSION

Patients with chronic anemia exhibit lower CBM signal intensity on MRI than healthy subjects. Patients with hemolytic anemia have thicker CBM than patients with non-hemolytic anemia or healthy individuals. Decreased CBM intensity may indicate that the patient has anemia, and increased CBM thickness may specifically point to hemolytic anemia. These MRI findings may signal the need for further evaluation for the clinician.

Megaloblastosis: from morphos to molecules

OBJECTIVE

Megaloblastosis (i.e., megaloblastic transformation of erythroid precursor cells in the bone marrow) is the cytomorphological hallmark of megaloblastic anemia resulting from vitamin B12 and folate deficiency. It is characterized by a finely stippled lacy pattern of nuclear chromatin, which is believed to be an expression of deranged cellular DNA synthesis. However, the molecular basis of these cytomorphological aberrations still remains obscure. The current presentation describes the results of our studies on some molecular events associated with the development of megaloblastosis.

METHODS

Transmission electron microscopy was used to study megaloblasts as well as DNA fibers extracted from megaloblastic and normoblastic bone marrows with and without treatment with proteinase K during the extraction procedure; cellular DNA synthesis in bone marrow cultures was studied by incorporation of 3H-thymidine and deoxyuridine suppression test, while histone biosynthesis in bone marrow cells was studied by in vitro incorporation of 3H-tryptophan, 3H-lysine and 3H-arginine into histones.

RESULTS

Derangement of DNA synthesis occurred due to an impaired de novo pathway of thymidylate synthesis in both vitamin-B12- and folate-deficient human megaloblastic bone marrows as well as in the bone marrows of rhesus monkeys and rats with experimentally induced folate deficiency. Interestingly, folate-deficient monkeys developed frank megaloblastic bone marrows, but folate-deficient rats did not. On the other hand, megaloblastic changes in the bone marrow of human patients with myelodysplastic syndrome and erythroleukemia were not associated with this DNA synthetic abnormality. Biosynthesis of predominantly arginine-rich histones in megaloblastic bone marrows was markedly reduced as compared to normoblastic bone marrows, which was consistently associated with elongation and despiralization of chromosomes and finely stippled nuclear chromatin in megaloblasts.

CONCLUSION

The impaired biosynthesis of predominantly arginine-rich nuclear histones appeared to be a common molecular event (a denominator) underlying the development of megaloblastosis with or without abnormal DNA synthesis.

[Histological changes of the distal ileum in chronic diarrhea associated with megaloblastic anaemia]

Histological changes of the distal ileum were evaluated in thirteen (13) patients suffering from chronic diarrhea associated with Megaloblastic Anaemia (MA). The patients were seven (7) men and six (6) women with an average age of 55.6 (34-74). They were all diagnosed with MA and treated with cianocobalamin and folic acid, which resulted in fast recovery. Follow up on the patients did not show any other cause related to chronic diarrhea. Biopsies from the distal ileum were taken by colonoscopy. Endoscopy findings were not relevant except for a light paleness or slightly-rough mucose. The following changes were found by examining the histological radiographies: chronic inflammatory infiltration 92% (12), intestinal villous atrophy 62% (8), erosions at villous surface 46% (6), slight ectasia of the lymphatics 46% (6), flattening of the epithelium cells of the villous 38% (5), and focal fibrosis 38% (5). The patients suffering chronic diarrhea associated with MA showed significant changes of the distal intestinal mucose (ileum). Those changes are probably also in the surrounding area and could explain not only the chronic diarrhea, but the poor absorption observed on some of the patients. The quick response to cobalamins and folates treatment showed the important role of these elements in intestinal restoration.

Defective RNA ribose synthesis in fibroblasts from patients with thiamine-responsive megaloblastic anemia (TRMA)

Fibroblasts from patients with thiamine-responsive megaloblastic anemia (TRMA) syndrome with diabetes and deafness undergo apoptotic cell death in the absence of supplemental thiamine in their cultures. The basis of megaloblastosis in these patients has not been determined. Here we use the stable [1,2-13C2]glucose isotope-based dynamic metabolic profiling technique to demonstrate that defective high-affinity thiamine transport primarily affects the synthesis of nucleic acid ribose via the nonoxidative branch of the pentose cycle. RNA ribose isolated from TRMA fibroblasts in thiamine-depleted cultures shows a time-dependent decrease in the fraction of ribose derived via transketolase, a thiamine-dependent enzyme in the pentose cycle. The fractional rate of de novo ribose synthesis from glucose is decreased several fold 2 to 4 days after removal of thiamine from the culture medium. No such metabolic changes are observed in wild-type fibroblasts or in TRMA mutant cells in thiamine-containing medium. Fluxes through glycolysis are similar in TRMA versus control fibroblasts in the pentose and TCA cycles. We conclude that reduced nucleic acid production through impaired transketolase catalysis is the underlying biochemical disturbance that likely induces cell cycle arrest or apoptosis in bone marrow cells and leads to the TRMA syndrome in patients with defective high-affinity thiamine transport.

Dietary folate deficiency with normal red cell folate and circulating blasts

This report describes a 26 year old woman, of Pakistani origin, who presented five months postpartum with severe megaloblastic anaemia as a result of nutritional folate deficiency. This case was unusual in that a small number of myeloblasts were present in the peripheral blood at presentation, and this circulating population temporarily increased in size when folate replacement was begun. We also highlight the need to recognise the non-linear relation between haematocrit and red blood cell folate concentration when the haematocrit is very low (< 0.15) and emphasise the importance of the clinical history.

[Four case reports of Biermer's anemia in West Africa]

The purpose of this report is to describe 4 cases of Biermer's anemia observed in West Africa over a 7-year period. Severe asthenia was the main clinical manifestation. Laboratory tests consistently demonstrated macrocytic anemia usually with a deep drop in hemoglobin levels ranging from 40 to 84 g/l associated with various degrees of thrombocytopenia or leukopenia. Other consistent findings were bone marrow megaloblastosis, serum vitamin B12 deficiency, and intrinsic factor antibodies. In most cases diagnosis was established on the basis of therapeutic tests with subsequent confirmation. Treatment using vitamin B12 therapy was successful in all cases. The authors recommend iron deficiency testing during the course of the disease and gastric biopsy during fibroscopy of upper digestive tract even if no macroscopic lesions are found.

Development of mice expressing a single D-type cyclin

D-cyclins (cyclins D1, D2, and D3) are components of the core cell cycle machinery. To directly test the ability of each D-cyclin to drive development of various lineages, we generated mice expressing only cyclin D1, or only cyclin D2, or only cyclin D3. We found that these "single-cyclin" embryos develop normally until late gestation. Our analyses revealed that in single-cyclin embryos, the tissue-specific expression pattern of D-cyclins was lost. Instead, mutant embryos ubiquitously expressed the remaining D-cyclin. These findings suggest that the functions of the three D-cyclins are largely exchangeable at this stage. Later in life, single-cyclin mice displayed focused abnormalities, resulting in premature mortality. "Cyclin D1-only" mice developed severe megaloblastic anemia, "cyclin D2-only" mice presented neurological abnormalities, and "cyclin D3-only" mice lacked normal cerebella. Analyses of the affected tissues revealed that these compartments failed to sufficiently up-regulate the remaining, intact D-cyclin. In particular, we found that in cerebellar granule neuron precursors, the N-myc transcription factor communicates with the cell cycle machinery via cyclins D1 and D2, but not D3, explaining the inability of D3-only mice to up-regulate cyclin D3 in this compartment. Hence, the requirement for a particular cyclin in a given tissue is likely caused by specific transcription factors, rather than by unique properties of cyclins.

Targeted disruption of Slc19a2, the gene encoding the high-affinity thiamin transporter Thtr-1, causes diabetes mellitus, sensorineural deafness and megaloblastosis in mice

Thiamin-responsive megaloblastic anemia syndrome (TRMA) is characterized by diabetes mellitus, megaloblastic anemia and sensorineural deafness. Mutations in the thiamin transporter gene SLC19A2 cause TRMA. To generate a mouse model of TRMA, we developed an Slc19a2 targeting construct using transposon-mediated mutagenesis and disrupted the gene through homologous recombination in embryonic stem cells. Erythrocytes from Slc19a2(-/-) mice lacked the high-affinity component of thiamin transport. On a thiamin-free diet, Slc19a2(-/-) mice developed diabetes mellitus with reduced insulin secretion and an enhanced response to insulin. The diabetes mellitus resolved after 6 weeks of thiamin repletion. Auditory-evoked brainstem response thresholds were markedly elevated in Slc19a2(-/-) mice on a thiamin-free diet, but were normal in wild-type mice treated on that diet as well as thiamin-fed Slc19a2(-/-) mice. Bone marrows from thiamin-deficient Slc19a2(-/-) mice were abnormal, with a megaloblastosis affecting the erythroid, myeloid and megakaryocyte lines. Thus, Slc19a2(-/-) mice have provided new insights into the TRMA disease pathogenesis and will provide a tool for studying the role of thiamin homeostasis in diabetes mellitus more broadly.

Folate and Vitamin B(12) deficiency presenting as pancytopenia in pregnancy: a case report and review of the literature

We present a case of extreme pancytopenia in a 27-year-old pregnant woman. The initial picture was compatible with a severe hematological problem in the category of aplastic anemia, paroxysmal nocturnal hemoglobinuria or even acute leukemia. The further biochemical investigations revealed, however, a folate deficiency. Nowadays this is a very rare cause of pancytopenia. Next to this she also had a Vitamin B(12) deficiency due to intrinsic factor failure. The recent literature is discussed.

A novel mutation in the SLC19A2 gene in a Tunisian family with thiamine-responsive megaloblastic anaemia, diabetes and deafness syndrome

Thiamine-responsive megaloblastic anaemia (TRMA) syndrome with diabetes and deafness was found in two patients from a Tunisian kindred. The proband was homozygous for a novel mutation, 287delG, in the high-affinity thiamine transporter gene, SLC19A2. We demonstrated that fibroblasts from this patient exhibited defective thiamine transport. These data confirm that the SLC19A2 gene is the high-affinity thiamine carrier and that this novel mutation is responsible for TRMA syndrome.

Apoptosis in megaloblastic anemia occurs during DNA synthesis by a p53-independent, nucleoside-reversible mechanism

Deficiency of folate or vitamin B(12) (cobalamin) causes megaloblastic anemia, a disease characterized by pancytopenia due to the excessive apoptosis of hematopoietic progenitor cells. Clinical and experimental studies of megaloblastic anemia have demonstrated an impairment of DNA synthesis and repair in hematopoietic cells that is manifested by an increased percentage of cells in the DNA synthesis phase (S phase) of the cell cycle, compared with normal hematopoietic cells. Both folate and cobalamin are required for normal de novo synthesis of thymidylate and purines. However, previous studies of impaired DNA synthesis and repair in megaloblastic anemia have concerned mainly the decreased intracellular levels of thymidylate and its effects on nucleotide pools and misincorporation of uracil into DNA. An in vitro model of folate-deficient erythropoiesis was used to study the relationship between the S-phase accumulation and apoptosis in megaloblastic anemia. The results indicate that folate-deficient erythroblasts accumulate in and undergo apoptosis in the S phase when compared with control erythroblasts. Both the S-phase accumulation and the apoptosis were induced by folate deficiency in erythroblasts from p53 null mice. The complete reversal of the S-phase accumulation and apoptosis in folate-deficient erythroblasts required the exogenous provision of specific purines or purine nucleosides as well as thymidine. These results indicate that decreased de novo synthesis of purines plays as important a role as decreased de novo synthesis of thymidylate in the pathogenesis of megaloblastic anemia.

Defective high-affinity thiamine transporter leads to cell death in thiamine-responsive megaloblastic anemia syndrome fibroblasts

We have investigated the cellular pathology of the syndrome called thiamine-responsive megaloblastic anemia (TRMA) with diabetes and deafness. Cultured diploid fibroblasts were grown in thiamine-free medium and dialyzed serum. Normal fibroblasts survived indefinitely without supplemental thiamine, whereas patient cells died in 5-14 days (mean 9.5 days), and heterozygous cells survived for more than 30 days. TRMA fibroblasts were rescued from death with 10-30 nM thiamine (in the range of normal plasma thiamine concentrations). Positive terminal deoxynucleotide transferase-mediated dUTP nick end-labeling (TUNEL) staining suggested that cell death was due to apoptosis. We assessed cellular uptake of [3H]thiamine at submicromolar concentrations. Normal fibroblasts exhibited saturable, high-affinity thiamine uptake (Km 400-550 nM; Vmax 11 pmol/min/10(6) cells) in addition to a low-affinity unsaturable component. Mutant cells lacked detectable high-affinity uptake. At 30 nM thiamine, the rate of uptake of thiamine by TRMA fibroblasts was 10-fold less than that of wild-type, and cells from obligate heterozygotes had an intermediate phenotype. Transfection of TRMA fibroblasts with the yeast thiamine transporter gene THI10 prevented cell death when cells were grown in the absence of supplemental thiamine. We therefore propose that the primary abnormality in TRMA is absence of a high-affinity thiamine transporter and that low intracellular thiamine concentrations in the mutant cells cause biochemical abnormalities that lead to apoptotic cell death.

Clinicopathological features of megaloblastic anaemia in Hong Kong: a study of 84 Chinese patients

Megaloblastic anaemia is uncommon in Hong Kong. Eighty-four consecutive Chinese patients with megaloblastic anaemia were studied. There were 48 males and 36 females, with a median age at presentation of 67 years. Vitamin B12 deficiency was found in all cases, with none of the patients showing folate deficiency. The frequency of pernicious anaemia in our patients was higher than in other south-east Asian series but comparable with western ones. When compared with patients in the West, our cases showed the following main differences: virtual absence of folate deficiency, even in alcoholics; absence of associated gastric malignancies; and a high frequency of tuberculosis.

Azathioprine-induced megaloblastic anemia with pancytopenia 22 years after living-related renal transplantation

Macrocytosis and megaloblastic changes in the bone marrow are frequently seen in renal transplant recipients treated with azathioprine (Az). However, severe anemia is a rare side effect of Az. We recently observed a case of severe megaloblastic anemia with pancytopenia in a renal transplant recipient who had been receiving Az therapy for 22 years. The patient was a 46-year-old woman who had been administered Az and prednisolone at a dose of approximately 1.7 mg/kg and 0.17 mg/kg daily, respectively. A bone marrow aspiration revealed megaloblastic anemia with the depletion of myeloid cells and megakaryocytes. She did not have vitamin B12 or folate deficiency. Therefore, FK506 (tacrolimus), a macrolide produced by Streptomyces tsukubaensis, which acts directly on T cells and is known to have less myelosuppression than Az, was substituted for Az. Although the leukopenia improved, the anemia and thrombocytopenia did not improve in the short term. She developed dyspnea and severe subcutaneous bleeding of the right lower extremity due to knee contusions. Hemodialysis was started to treat her uremic state. Although it was impossible to evaluate the long-term effects of FK506 therapy for the pancytopenia in our case, the conversion from Az to a less myelosuppressive drug, such as FK506, should be considered in renal transplant recipients with severe myelosuppression caused by long-term Az treatment.

Apoptosis of late-stage erythroblasts in megaloblastic anemia: association with DNA damage and macrocyte production

An in vitro model of folate-deficient erythropoiesis has been developed using proerythroblasts isolated from the spleens of Friend virus-infected mice fed an amino acid-based, folate-free diet. Control proerythroblasts were obtained from Friend virus-infected mice fed the same diet plus 2 mg folic acid/kg diet. Our previous studies showed that, after 20 to 32 hours of culture in folate-deficient medium with 4 U/mL of erythropoietin, the folate-deficient proerythroblasts underwent apoptosis, whereas control erythroblasts survived and differentiated into reticulocytes over a period of 48 hours. The addition of folic acid or thymidine to the folate-deficient medium prevented the apoptosis of the folate-deficient erythroblasts, thereby implicating decreased thymidylate synthesis as the main cause of apoptosis in the folate-deficient erythroblasts. In the study reported here, we examined intracellular folate levels, uracil misincorporation into DNA, p53 and p21 proteins, and reticulocyte formation in erythroblasts cultured in folate-deficient or control medium. In all experiments, the folate-deficient erythroblasts cultured in folate-deficient medium gave results that varied significantly from folate-deficient erythroblasts cultured in control medium or control erythroblasts cultured in either folate-deficient or control media. Folate-deficient erythroblasts cultured in folate-deficient medium had marked decreases in all coenzyme forms of folate that persisted throughout culture, increased uracil misincorporation into DNA, persistent accumulations of p53 and p21, and decreased reticulocyte production but increased size of individual reticulocytes. A model of folate-deficient erythropoiesis based on apoptosis of late stage erythroblasts is presented. This model provides explanations for the clinical findings in megaloblastic anemia.

Evaluation of DNA analysis for evidence of apoptosis in megaloblastic anaemia

This study involved DNA analysis of bone marrow cells of 15 patients with megaloblastic anaemia. The diagnosis was based on the morphological changes seen in the bone marrow, associated with either a low red cell folate or serum vitamin B12 level and an adequate response to appropriate therapy as confirmation of the diagnosis. Flow cytometric DNA analysis showed an increase in the S and G2 phases of the cell cycle, but conventional agarose gel electrophoretic DNA analysis did not confirm the characteristic 'ladder pattern' which might have been expected in classic apoptosis. In addition, cells showing morphological changes suggestive of apoptosis, such as nuclear condensation and fragmentation, did not show evidence of DNA fragmentation using the ApopTag in situ digoxigenin nucleotide labelled, peroxidase detection system. Further studies using annexin V flow cytometric analysis and pulsed field gel electrophoresis were also unable to detect evidence of apoptosis as a significant cause of cell death in megaloblastic anaemia.

Visual evoked responses in megaloblastic anemia

Pattern shift visual evoked responses (PSVER) were studied in thirty patients suffering from severe megaloblastic anemia (mean Hb level was 4.25 +/- 1.22 g/dL) of nutritional origin. All patients lacked clinical stigmata of visual and neurologic impairment. Mean P100 latency in thirty age and sex matched controls was 96.35 +/- 6.75 ms (range 86-108 ms) and mean amplitude was 10.37 +/- 3.88 microV (range 4.8-20.8 microV). Mean P100 latency in megaloblastic anemia was 114.77 +/- 11.68 (range 91-142) ms, P < 001 vs. control) and mean amplitude was 8.85 +/- 2.8 microV (range 5.1-16.2 microV). Seventy percent cases had prolonged latency of P 100. After correction of anemia with therapeutic doses of vitamin B12 and folic acid in three months (mean Hb level was 12.08 +/- 1.86 g/dL), the mean P100 latency was 105.13 +/- 9.30 ms (range 92-121 ms P < 0.001 vs. controls) and mean amplitude was 10.72 +/- 4.13 microV (range 5.1-21.4 microV). There was significant improvement in P100 latency after correction of anemia (P < 0.01). There was a negative correlation between P100 latency and hemoglobin levels, though it was statistically not significant.

Nucleic acid composition of bone marrow mononuclear cells in cobalamin deficiency

Recent studies using anion exclusion chromatography have suggested that uracil is misincorporated into the DNA of patients with megaloblastic anemia to levels detectable by nonradioactive methods. We have investigated the nucleotide composition of DNA from the bone marrow mononuclear cells of eight patients with cobalamin deficiency and compared this with that found in normal subjects. The median level of uracil in the megaloblastic group was 0.082 mol% of cytosine (approx. 0.02 mol% of all bases in DNA), which was similar to that found in the control group (median 0.085 mol% of cytosine) and may be attributable, at least in part, to artefactual deamination of deoxycytidine monophosphate during the DNA hydrolysis. Our findings give no support for the view that, by overwhelming the uracil N-glycosidase mechanism, the degree of uracil misincorporation in megaloblastic anemia is sufficient to increase the steady state level of uracil in the DNA by amounts detectable by nonradioactive methods. Using high performance liquid chromatography, we have also demonstrated normal levels of methylcytosine in the DNA of megaloblastic subjects.

[Megaloblastic anemia: 30 cases in a district hospital]

The high incidence of megaloblastic anemia observed at our institution (2.1% of hospital admissions) prompted us to analyze the causes of cobalamin and/or folate deficiency in 30 patients admitted during the period 1983-1991 to the Medical Department of Locarno District Hospital. The study population includes 19 women and 11 men with a mean age of 69 years (range 28-91 years). All patients had severe macrocytic anemia (mean hemoglobin 74 +/- 23 g/l, MCV 121 +/- 12 fl), striking megaloblastic changes in aspirated marrow, and an elevated serum level of LDH (2170 +/- 2150 U/l). 19 patients had associated thrombocytopenia, 12 leukopenia and 11 both thrombocytopenia and leukopenia. Treatment led to prompt reticulocytosis and correction of megaloblastic changes in all patients, as well as to nearly complete resolution of the neurologic disorder in a patient with severe spastic ataxia. In 15 patients, megaloblastic anemia was caused by folate deficiency related to alcoholism (n = 6, mean age 55 years) and old age or poverty (n = 9, mean age 73 years). Cobalamin deficiency was present in 9 patients (mean age 69 years); it was due to pernicious anemia in 6 patients and to malabsorption in 2, while the cause remained unexplained in 1. The last patients (mean age 76 years) had deficiency of both cobalamin and folate, related to alcoholism (n = 3) or poverty (n = 3).

[Megaloblastic anemia associated with chronic diarrhea. A prospective and multicenter study in Lima]

Since 1986 we have been observing an increased number of patients with megaloblastic anaemia (MA) associated to chronic diarrhea. In 60% of the cases we could not identify any etiologic factor. In the last three years a prospective study in Lima (Peru) has been carried on aimed to investigate this aspect; patients with diseases recognized to be associated to MA were excluded. 45 patients were included age average 37.5 years, all of them have a confirmed diagnosis by bone marrow; 64% with low serum B12 and folic acid, 20% with low serum B12, and 16% with low serum folic acid. Gastric biopsies did not show atrophy in 67%; intragastric pH was lower than 4 in 50% duodenal content culture was positive in 35% (6/17) to aerobic gram negative agents; 62% (5/8) of duodenal biopsies, 83% (5/6) of jejunal biopsies, 4/4 (100%) of ileal biopsies, showed diverse structural changes; 100% did not show Diphyllobothrium pacificum. All these findings make us suggest that a significative number of patients with MA and chronic diarrhea in Lima are related to small bowel bacterial overgrowth. These bacteria can "sequestrate" or consume folates and cobalamines besides the direct damage they can cause to intestinal morphology. Future studies are needed to confirm our proposal and define if these cases belong to a variety of tropical sprue.

Imerslund-Gräsbeck syndrome in two brothers: renal biopsy and ultrastructural findings

In two Chinese siblings with Imerslund-Gräsbeck syndrome, light microscopy of renal biopsies showed no remarkable change. Ultrastructurally, there were small possible focal defects in the glomerular basement membrane. Neither podocytes nor tubular cells showed evident change. No electron dense deposit was found. Our observations on renal ultrastructure differ from the previous five reports. The literature on renal pathology of this syndrome is reviewed.

Cytoplasmic vacuolization of enterocytes: an unusual histopathologic finding in juvenile nutritional megaloblastic anemia

We report a case of juvenile nutritional megaloblastic anemia with emphasis on the histologic findings in the upper gastrointestinal system, including the previously unreported feature of periodic acid-Schiff (PAS)-negative, Alcian blue-negative cytoplasmic vacuoles (CV) in duodenal enterocytes. These CV were reminiscent of those described in abetalipoproteinemia; however, the patient's lipid profile was normal. All histopathologic changes in the upper gastrointestinal tract (with the exception of mild reflux esophagitis) reverted to normal following parenteral administration of vitamin B12. This case supports the notion that CV in enterocytes are a component (albeit a rare one) of the histopathology in cobalamin deficiency.

[Ultrastructural study of the megakaryocytes in megaloblastic anemia]

The ultrastructure of the megakaryocytes in the bone marrow from 14 cases of megaloblastic anemia was studied. The commonest change observed was that the development of the nucleus lagged behind that of the cytoplasm. There were some evidences supporting the theory of ineffective thrombocytopoiesis. The mechanism of the relationship between the changes of morphology and function based on the impaired DNA synthesis and methylation due to folate and vitamin B12 deficiency were also discussed.

Bone marrow iron in nutritional anaemias

Bone marrow smears of 168 patients with nutritional anaemias attending the Dr. J.C. Patel, Department of Hematology, K.E.M. Hospital were stained by Prussian blue method for iron (haemosiderin). Iron in the bone marrow was classified as absent, decreased, normal or increased. Amongst 93 cases with transferrin saturation (TS) of less than 16% and normoblastic erythropoiesis, bone marrow iron was absent in 48 (51.6%) and decreased in 45 (48.4%). In 50 cases with TS of less than 16% and marrow showing megaloblasts and/or giant myelocytes and metamyelocytes, bone marrow iron was absent in 15 (30%), decreased in 22 (44%), normal in 7 (14%) and increased in 6 (12%). In 25 cases with TS over 16% and megaloblastic erythropoiesis, bone marrow iron was absent in 4 (16%), decreased in 1 (4%), normal in 7 (28%) and increased in 13 (52%). In 150 (89.3%) patients out of 168, bone marrow iron and TS gave concordant results whereas in 18 (10.7%), the results were discordant; former was encountered in cases of uncomplicated iron deficiency while latter was found with megaloblastic morphology of the marrow. It is concluded that there is a good correlation between TS and bone marrow iron and hence, either of the criteria can be used for the diagnosis of iron deficiency especially when it is not complicated by megaloblastosis.

Thymidylate synthesis and utilization via the de novo pathway in normal and megaloblastic human bone marrow cells

We have measured the thymidylate synthetase activity of intact bone marrow cells using a 3H2O release assay. The mean thymidylate synthetase activity of vitamin B12- or folate-deficient megaloblastic marrow cells was reduced only in severely anaemic patients. There was a correlation between thymidylate synthetase activity and RBC in patients with megaloblastic haemopoiesis. The mean rate of incorporation into DNA of 6-3H deoxyuridine was similar in megaloblastic and normoblastic marrows. The rate of thymidylate synthesis exceeded its incorporation into DNA in all marrows, and the mean ratio between synthesis and incorporation was similar in normoblastic and megaloblastic patients, being independent of both thymidylate synthetase activity and RBC. Thus de novo thymine nucleotides were not utilized more efficiently in megaloblastic marrow cells. These data suggest that impaired thymidylate synthesis may not be the central defect in megaloblastic haemopoiesis, and that there is only a single pool of thymidine triphosphate in human bone marrow cells.

The bone marrow in nutritional deficiencies

The overwhelming majority of nutritional deficiencies that affect the bone marrow and blood are due to the lack of vitamin B12, folic acid, or iron or combinations thereof. The two vitamins are closely related in DNA synthesis, whereas iron is the most abundant heavy metal in the body and is chiefly utilized for hemoglobin synthesis. Concomitant conditions of vitamin B12 and/or folate deficiency along with iron deficiency are not infrequent, and one type of anemia may mask the other. It is important to establish the correct diagnoses, as therapy directed at the wrong deficiency may hide the real deficiency with disastrous results. Specific diagnostic tests are now available to determine definitive diagnoses, and specific therapy is readily available to restore and maintain a normal nutrient status.

Erythromyeloid lineage fidelity is conserved in erythroleukaemia

Blast cells from eight patients with erythroleukaemia and one with erythroid blast crisis of chronic myeloid leukaemia were studied for the co-expression of cell surface myeloid and erythroid markers, and the phenotype compared with that of erythroblasts from two patients with megaloblastic anaemia. The technique of dual indirect immunofluorescence was used with a panel of seven mouse monoclonal antibodies against well-defined myeloid antigens (CD11b, 13, 14, 15, 33 and HLA-DR) and a rat antibody, YTH89.1, specific for glycophorin A. No dual fluorescence, emanating from myeloid or erythroid lineage markers, was found to occur in either the neoplastic or non-neoplastic erythroid cells studied. These data support the hypothesis that lineage fidelity is conserved in leukaemia.