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Bone and marrow are the two facets of the same organ, in which bone and hematopoietic cells coexist and interact. Marrow and skeletal tissue influence each-other and a variety of genetic disorders directly targets both of them, which may result in combined hematopoietic failure and skeletal malformations. Other conditions primarily affect one organ with secondary influences on the other. For instance, various forms of congenital anemias reduce bone mass and induce osteoporosis, while osteoclast failure in osteopetrosis prevents marrow development reducing medullary cavities and causing anemia and pancytopenia. Understanding the pathophysiology of these conditions may facilitate diagnosis and management, although many disorders are presently incurable. This article describes several congenital bone diseases and their relationship to hematopoietic tissue., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background/aims: Population-based registries play a key role in the epidemiological surveillance of congenital anomalies (CAs). This study is aimed at improving the epidemiological surveillance and providing prevalence estimates of rare CAs using the Registry of Rare Diseases as an added data source to the Registry of Congenital Anomalies., Methods: Cases of diagnosed rare CAs (2006-2013) were extracted from the Tuscany Registry of Rare Diseases and the Tuscany Registry of Congenital Anomalies in order to set up an integrated dataset. Prevalence (per 100,000 births; 95% confidence interval) was calculated for each rare CA., Results: Overall, 56 rare CAs were analyzed including 656 cases, of whom 121 (18.4%) were retrieved from the Registry of Rare Diseases that provided a major contribution for rare CAs for which a prenatal diagnosis is difficult, or for CAs more easily diagnosed in the postneonatal period. After data integration, an increased prevalence estimate was observed in particular for atresia of bile ducts (6.24; 3.57-10.14), tuberous sclerosis (2.34; 0.86-5.10), Kabuki syndrome (1.95; 0.63-4.55), and some monogenic CAs., Conclusions: This study represents an example of integration of registries operating in the field of rare diseases. Providing the accurate prevalence of rare CAs is a key point to improving surveillance, supporting public health policies, and planning healthcare., (© 2017 S. Karger AG, Basel.)

Haematopoietic stem cell transplantation (HSCT) remains the best therapeutic option for many acquired and inherited paediatric haematological disorders. Unfortunately, the probability of finding an HLA matched donor is limited. An alternative technique is PGD combined with HLA matching, which offers the possibility of selecting unaffected embryos that are HLA compatible with the sick child, with the aim of possible use of stem cells from the resulting baby in future. Since the first successful report for Fanconi anaemia a decade ago, the therapeutic success of this technique was reported in a few cases and for a limited number of disorders. Here, we report full recovery of 44 sick children who received HSCT from healthy infants conceived after pre-implantation HLA matching for the following 10 indications; beta-thalassaemia, Wiskott-Aldrich syndrome, Fanconi anaemia, sickle cell anaemia, acute myeloid leukaemia, acute lymphoblastic leukaemia, Glanzmann's thrombasthaenia, Diamond-Blackfan anaemia, X-linked adrenoleukodystrophy and mucopolysaccharidosis type I. No serious complications were observed among recipients and donors. Graft failure occurred in four children with beta-thalassaemia where a second HSCT was planned. Preimplantation HLA matching is a reliable technique and provides a realistic option for couples seeking treatment for an affected child when no HLA-matched donor is available., (Copyright © 2014 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.)

Neonatal lupus erythematosus (NLE) is characterized by the transplacental passage of maternal anti-Ro and/or anti-La antibodies and characteristic illnesses in the foetus/neonate. Most attention has focused on the most serious complication- cardiac involvement. This article will focus on non-cardiac involvement. Skin involvement (cutaneous NLE) is present in 15-25% of children with NLE. The rash of NLE tends to be photosensitive but may be present at birth or in non-sun exposed areas. It is most frequently seen around the eyes, not in the malar area, but also occurs in other parts of the body. The pathology resembles the rash of subacute cutaneous lupus erythematosus. Anti-Ro antibodies are present in >95% with the remaining mothers having anti-U1RNP antibodies only. Asymptomatic elevation of liver function tests, which may be associated with evidence of cholestasis, is seen in 10-25% of cases of NLE. Mild hepatomegaly and less commonly splenomegaly may be present. Liver involvement seen in isolation or associated with other features. The pathology resembles idiopathic neonatal giant cell hepatitis. Any haematological lineage, neutropenia and thrombocytopenia most commonly, may be affected by NLE. Haematological involvement is almost always asymptomatic. There are protean manifestations of neurologic involvement in NLE: hydrocephalus, non-specific white matter changes, calcification of the basal ganglia and a 'vasculopathy'. The most unusual feature of NLE is the radiographic finding of stippling of the epiphyses (chondrodysplasia punctata). Overall, non-cardiac involvement of NLE is more common than cardiac. The study of these manifestations may lead to new insight into how autoantibodies lead to disease.

Glucocorticoids (GCs) are known for their clinically useful effects in immunologic and inflammatory disorders. Although there is a huge volume of knowledge concerning the cellular and molecular effects of GCs, statements regarding their effects in multiple diseases at variable doses are not clear-cut owing to pharmacogenetic differences. The main actions of GCs in hematologic disorders have been related to their differentiation-inducing and apoptosis-inducing effects, but modification of several steps of the hematopoietic and/or immune pathway has also been reported. In our clinic, mega-dose methylprednisolone (MDMP) has been successfully used for treatment of different hematologic diseases, such as leukemias, bone marrow failure in aplastic anemia, hypoplastic anemia, myelodysplastic syndrome, neutropenia, autoimmune diseases, and in some congenital hereditary diseases. Both clinical and experimental studies in our department revealed that MDMP was more effective than conventional dose steroids. It is interesting that MDMP can be curative in some congenital hereditary diseases such as Diamond-Blackfan syndrome. However, more research is required to clarify their roles in biology, physiology, and molecular genetics.

Neonatal hematology is a complex subspecialty of pediatric hematology, combining the unique aspects of the maternal/fetal relationship, the delicate balance of coagulation factors, and the distinctive physiologic conditions of the newborn period. The objective of this article is to briefly review specific hematologic disorders that commonly present in the newborn period. Alloimmune cytopenias, polycythemia, thrombosis and bleeding associated with vitamin K deficiency will be discussed through a focus on pathophysiology, signs and symptoms, current treatment strategies, and implications for nursing care.

Neonatal Lupus Syndrome is a rare disease caused by placental passage of maternal autoantibodies. Pathogenesis is partially unknown and many clinical manifestations are possible. We report on newborn siblings who presented with different symptoms of Neonatal Lupus Syndrome. One patient presented with congenital heart block and another with hepatic and haematologic involvement. Cases of Neonatal Lupus among siblings are very rare, because of the high risk of pregnancy in affected women. Various clinical expressions may be explained by a different specificity of Anti-Ro autoantibodies among siblings. The reported cases are commented with regard to recent literature, trying to explain their pathogenesis.

The treatment of congenital hematologic disorders before birth by in utero hematopoietic stem cell transplantation remains a challenging goal. Although success has been achieved in X-linked severe combined immunodeficiency, the approach has failed in all other disorders attempted thus far. In this review, we examine relevant experimental data from the perspective of an analysis of why failure has occurred. We will also attempt to pose the important questions that will need to be answered prior to further clinical attempts to treat most target disorders by this approach., (Copyright 2004 S. Karger AG, Basel)

Over the last decade, the majority of inborn errors of haematopoiesis has been elucidated on a molecular level. For some of these diseases, gene transfer into transplantable cells offers new therapeutic perspectives. Improved retroviral or lentiviral techniques allow stable gene transfer in >10% of repopulating cells cultured in vitro. However, severe impediments are still encountered with respect to achieving sufficient and long-lasting transgene expression levels and appropriate numbers of transgenic cells in vivo. Improving the techniques for manipulation of stem cells in vitro, and the development of regimens promoting engraftment and selection of gene-modified cells are important areas of current research. Further activities address the level and persistence of transgene expression within individual cell clones, and the functional characteristics of progeny cells in vivo. Promises with respect to the potential impact of gene therapy for patients suffering from inherited disorders are often triggered by 'proof of concept' in preclinical disease models. However, recent observations of side effects related to random vector insertion or transgene expression indicate that even more careful quantitative and qualitative investigations of efficiency and toxicity may be needed for individual transgenes before approaching clinical trials.

Hematopoietic stem cells constitute a rare population of precursor cells with remarkable properties for being used as targets in gene therapy protocols. The last years have been particularly productive both in the fields of gene therapy and stem cell biology. Results from ongoing clinical trials have shown the first unquestionable clinical benefits of immunodeficient patients transplanted with genetically modified autologous stem cells. On the other hand, severe side effects in a few patients treated with gene therapy have also been reported, indicating the usefulness of further improving the vectors currently used in gene therapy clinical trials. In the field of stem cell biology, evidence showing the plastic potential of adult hematopoietic stem cells and data indicating the multipotency of adult mesenchymal precursor cells have been presented. Also, the generation of embryonic stem cells by means of nuclear transfer techniques has appeared as a new methodology with direct implications in gene therapy.

This review summarizes state-of-the-art and emerging techniques in the antenatal diagnosis of fetal anemia and hemoglobinopathies. Fetal anemia may result from hemolytic disease, hemorrhage, suppression of erythropoiesis, infection (eg, parvovirus B19), or trauma. The clinical laboratory plays an essential role in the evaluation of these disorders by way of the use of various hematologic, biochemical, serologic, cytometric, and molecular genetics methods. Hemoglobinopathies are the most common class of single gene disorders worldwide. The authors have used the example of homozygous alpha-thalassemia major (Hb Barts disease) as a paradigmatic case for antenatal hemoglobinopathy screening. Perhaps the most familiar indication for hematologic screening in pregnancy is HDFN, most commonly in pregnancies previously sensitized to the RhD antigen. All pregnant women, regardless of their past medical or obstetric history or previous antibody screens, should have ABO/Rh blood typing and a red cell antibody screen performed at the first prenatal visit. Long-established methods for assaying FMH (KB method), microcytosis (hemogram with red cell indices), and blood group incompatibility (direct antigen test, serologies) remain critical for rapid, sensitive diagnosis. Analysis of fetal free DNA in maternal plasma holds the promise for rapid, ultrasensitive, and noninvasive detection of many fetal hematologic disorders.

The prevalence of familial plasminogen deficiency in Scotland has recently been calculated at 2.9/1000. However, little is known of the molecular genetic background and the frequency of plasminogen gene mutations in most cases of inherited plasminogen deficiency. Having previously identified 28 unrelated subjects with familial plasminogen deficiency from a cohort of 9611 blood donors, we have now reviewed 19 of these 28 subjects and screened the plasminogen gene in 15 subjects with hypoplasminogenaemia (plus five relatives) and four subjects with dysplasminogenaemia for mutations and polymorphisms. A missense mutation K19E in the plasminogen gene was found in 13 of the 15 propositi with hypoplasminogenaemia, in one of these in a homozygous manner. In two subjects with hypoplasminogenaemia, two new mutations (P353A and R471X) were identified. These three different mutations, if inherited in a homozygous or compound-heterozygous manner, may be associated with the development of ligneous conjunctivitis. In four subjects with dysplasminogenaemia, three heterozygous mutations (C548G, n = 1; A601T, n = 1; G693R, n = 2) were found. None of the propositi with plasminogen deficiency developed venous thrombosis at any time. In conclusion, the K19E mutation in the plasminogen gene is a common cause of hypoplasminogenaemia in Scotland, with an estimated prevalence of around 0.14%.

Apoptosis, the cell's intrinsic death program, plays a critical role in the regulation of tissue homeostasis, especially in cell systems with a high turnover rate such as hematopoiesis. Imbalances between survival, proliferation and death of precursor cells or mature cells may result in accelerated loss or impaired output or uncontrolled polyclonal or monoclonal expansion and may pave the way to the development of leukemia. Congenital hematologic disorders are characterized by disturbed growth control of hematopoietic cells. In the previous years, it has become clear that deregulated apoptosis contributes or is even a key determinator of the pathophysiology of diseases such as lymphoproliferation, aplastic anemia or chronic neutropenia. Hematopoietic growth factors have been shown not only to stimulate proliferation of hematopoietic stem cells and committed precursor cells, but also to act as survival factors protecting developing precursor cells from apoptotic signals. The molecular delineation of pathways of apoptosis signaling or survival in hematopoietic cells is expected to provide tools for molecular understanding of the pathophysiology of congenital and acquired hematopoietic disorders and to identify targets for therapeutic intervention strategies.

In the research we showed some inborn syndromes with disturbances of the neutrophils' number. The diseases were divided in the following categories: disturbed proliferation of myeloid stem cells, phenotypic anomalies, panmyelophtisis, neutropenia caused of marrow infiltration, neutropenia caused of agammaglobulinemia or dysgammaglobulinemia, metabolic disorders. The nowadays diagnostic possibilities and treatment in these cases were showed.

Advances in prenatal diagnostic techniques allow for earlier, more rapid, and more effective detection of congenital disorders. The indications, diagnostic accuracy, and risks for invasive diagnostic techniques including amniocentesis, chorionic villus sampling, and fetal blood sampling are reviewed. Recent advances in non-invasive detection methods, such as fetal ultrasound and the isolation of fetal cells in the maternal circulation are discussed. Additionally, the intrauterine diagnosis of congenital infections and chromosomal and Mendelian disorders, as well as hematologic disorders are summarized.

Four patients with congenital dyserythropoiesis characterized by marked macrocytosis, little or no anaemia, and vitamin B12- and folate-independent megaloblastic erythropoiesis are reported. Their erythroblasts also showed various dysplastic changes but not those diagnostic for congenital dyserythropoietic anaemia (CDA) types I or III. The haematological features of the four patients, who included two siblings, resemble those of a previously reported patient and together these patients form a recognizable subgroup within those cases of CDA not belonging to CDA types I-III. In two of the cases studied, and possibly a third, the inheritance was as an autosomal recessive character.

Congenital hemolytic anemias resulting from PK, PFK, and G6PD enzyme deficiencies have been reported in domestic animals. Dogs with PFK deficiency may have episodes of intravascular hemolysis with hemoglobinuria in addition to a persistent compensated hemolytic anemia. Patients with mild G6PD deficiency are not anemic but may show increased susceptibility to oxidant-induced erythrocyte injury. Persistent methemoglobinemia has been reported in dogs and cats with methemoglobin reductase enzyme deficiency. Affected animals have cyanotic-appearing mucous membranes but show no or only mild clinical signs attributable to hypoxemia. Enzyme assays are usually done after acquired causes of hemolytic anemia and methemoglobinemia have been ruled out.

History: A 26-year-old man sustained a wasp bite 5 years ago which caused arterial embolism to the right brachial artery. Now he again had a wasp bite with allergic reaction and an arterial embolus to the left brachial artery. 2 days later, after embolectomy and heparinisation, he had a cerebrovascular accident due to an embolus to the left internal carotid artery. 15 days later, despite oral anticoagulation (Quick value 10%), he had an embolism to the left femoral artery., Investigations: The source of the emboli was found by echocardiography to be a spherical floating thrombus on the aortic valve. The plasminogen level was only 45-61%. His mother and sister also had a low plasminogen level, i.e. he had congenital plasminogen deficiency., Treatment and Course: At surgery, when the thrombus had been removed, a slit-like defect was found on one of the aortic leaflets and covered with a pericardial patch. At first heparin then phenprocoumon were administered, plus 250 mg ticlopidine twice daily. There have been no further complications., Conclusion: As the patient's fibrinolysis activity was normal, additional, probably allergic, factors must have been present to disturb the equilibrium between thrombogenesis and fibrinolysis thus causing thrombosis at a predisposed site.

In utero fetal stem cell transplantation represents a new and still experimental therapeutic strategy for diseases related to the hematopoietic system. The broad therapeutic implications as well as potentials and limitations of this new technique are presented. To date, 6 cases of fetus-to-fetus transplantation have been published in the literature.

A case of acute promyelocytic leukemia (APL) developed in a patient with congenital antithrombin III (AT-III) deficiency is reported. Despite the presence of disseminated intravascular coagulation (DIC), plasma AT-III activity was not decreased at the diagnosis of APL compared to the patient's baseline level (approximately 50% of normal). He was successfully treated with all-trans retinoic acid (ATRA) to achieve complete remission without the use of heparin. Although he developed phlebitis at the site of insertion of the intravenous catheter during remission-induction, no major thrombotic episode was noted. Coagulation parameters including fibrin and fibrinogen degradation products (FDP-E), thrombin-antithrombin complex (TAT), FDP-D dimer (D-D dimer), and plasmin-alpha 2 plasmin inhibitor complex (PIC) improved rapidly after initiation of ATRA. This case is a clear demonstration of the characteristics of DIC developing in APL, i.e. no or minimal decrease in the level of AT-III activity and a predominant increase in the fibrinolytic system, rather than hypercoagulability.

Platelet-derived growth factor (PDGF) affects the growth, migration, and function in vitro of mesenchymal cells, but little is known about its normal physiological functions in vivo. We show here that mice deficient for PDGF B die perinatally and display several anatomical and histological abnormalities. Kidney glomerular tufts do not form, apparently because of absence of mesangial cells. Instead, a single or a few distended capillary loops fill the glomerular space. The heart and some large arteries dilate in late-stage embryos. Most PDGF B mutant embryos develop fatal hemorrhages just prior to birth. Their hematological status includes erythroblastosis, macrocytic anemia, and thrombocytopenia. On the basis of these findings, we conclude that PDGF B has crucial roles in vivo in establishing certain renal and circulatory functions.

In the present study, the prevalence of thromboembolic events in patients suffering from type I plasminogen deficiency was evaluated. One hundred and twelve affected subjects belonging to twenty-eight kindreds were gathered from the literature and from personal observations. The incidence of thrombosis found in this group was compared with those seen in: a) 86 unaffected family members; b) 100 hospitalized patients; c) 100 outpatient clinic patients. In the latter two groups, congenital clotting disorders were excluded. Thrombotic manifestations were found in 25.8% of patients with plasminogen deficiency, a figure which was statistically different from those found in unaffected family members (1.16%, p < 0.001), hospitalized patients (3%, p < 0.001) and outpatient clinic patients (5%, p < 0.001). In twenty-four kindreds with hypoplasminogenemia, data concerning the actuarial ages at first thrombotic event were available for construction of thrombosis-free survival curves by the Cutler-Ederer method. The difference between the two curves, corresponding to affected and unaffected family members respectively, were statistically significant (p < 0.01). In conclusion, although the incidence of thromboembolic events in type I plasminogen deficiency is certainly lower than that described in other congenital clotting disorders such as AT III, protein C and protein S, patients with hypoplasminogenemia should be considered at risk for thrombosis, particularly when triggering factors are present.

The insight in the function and dysfunction of granulocytes lately arouses more and more interest. This report summarises our present knowledge. In the first of two chapters the authors review the molecular basis of granulocyte function and the inborn defects of chemotaxis, opsonisation, phagocytosis and intracellular killing of bacteria and fungi.

Dyskeratosis congenita (DC) is a rare familial hematologic disorder that has various modes of inheritance. We have studied 2 siblings with DC. 1 sibling had thrombocytopenia, which responded to therapy with nandrolone decanoate and oxymetholone. Platelets were abnormally small, which indicates that a qualitatively abnormal megakaryocytopoiesis is a feature of DC. Myeloid and erythroid progenitors in specimens of the blood and bone marrow from both siblings were either absent or greatly reduced in numbers. The qualitatively abnormal megakaryocytopoiesis, and the quantitative abnormality of hematopoietic progenitor cells committed to myelopoiesis and erythropoiesis, indicates involvement of the pluripotent stem cell in DC. Cytogenetic studies of the bone marrow and peripheral blood lymphocytes from these patients showed normal karyotypes, a normal sister chromatid exchange frequency, and a rapid proliferation of peripheral T lymphocytes, a feature of the disorder that has not been reported previously.

This review has concentrated on clinical syndromes for which a congenital basis of polymorphonuclear neutrophil dysfunction has been identified. The first clinical syndrome found to be associated with dysfunctional polymorphs was chronic granulomatous disease of childhood. Identification of a cellular defect in oxidative metabolism and microbicidal activity of polymorphonuclear neutrophils from patients with CGD stimulated intense investigation of the function of phagocytes in several clinical entities characterized by increased susceptibility to infection. Other diseases with a probable congenital basis for polymorph dysfunction include Chediak-Higashi syndrome, myeloperoxidase deficiency, severe glucose-6-phosphate dehydrogenase deficiency, and Down's syndrome. Functional defects have also been identified in neutrophils with morphologic abnormalities, such as the Pelger-Huet anomaly and the May-Hegglin anomaly, and in neutrophils without alkaline phosphatase or with a disorder of the glutathione system. The evidence for a relation between these cellular disorders and susceptibility to infection is tentative. Patients with congenital disorders of polymorphonuclear neutrophil microbicidal function frequently suffer prolonged infections in spite of appropriate antimicrobial therapy, and severe lesions recur with discouraging frequency. These lesions are usually soft tissue or bone abscesses, and the etiologic agents are typically staphylococci, gram-negative enteric species, or fungi. The infectious disease problems of patients with phagocytic cell disorders are usually quite distinct from the problems of patients without immunoglobulins or with complement deficiency. Patients with agammaglobulinemia, for example, suffer recurrent septicemia or meningitis due to Streptococcus pneumonia or H. influenzae. Septicemia, especially with the pyogenic bacterial species, is unusual in patients with polymorphoinuclear dysfunction. A major contribution of the currently intense investigation of cells from patients with congenital disorders of phagocyte function has been the greatly increased understanding of the molecular events necessary for the normal function of these cells. The role of the oxidative metabolic burst during phagocytosis has been clearly identified as essential to the microbicidal function of polymorphs and monocytes, and the glutathione system has been identified as essential to the regulation of these oxidative reactions. It is anticipated that these studies may lead to practical methods for "stimulating the phagocytes" in patients with increased susceptibility to infection.

Neutrophil specific granules are thought to be important in the evolution of the inflammatory response. Specific granules are preferentially released with minor membrane perturbation in vitro or in vivo, and secreted products probably have important effects on humoral and cellular components of inflammation. In vitro studies reveal that some secreted specific granule products activate the complement cascade to generate the chemoattractant C5a and the opsonin C3b, while other secreted products are selectively chemotactic for monocytes. Translocation of receptors for chemoattractants (fmet-leu-phe) and opsonins (C3bi) from specific granules or closely related organelles to the plasma membrane may play an important role in chemotaxis, adherence, and phagocytosis. Similar translocation of constituents of the electron transport chain involved in the respiratory burst (i.e. cytochrome b) probably plays a role in neutrophil oxidative metabolism and hydrogen peroxide generation. In vivo and in vitro studies of neutrophils from patients with congenital specific granule deficiency, acquired specific granule deficiency (thermal injury and neonates), or normal neutrophils experimentally depleted of nuclei and organelles support these conclusions. Thus, release of specific granule constituents appears to be important for amplification of the initial and subsequent phases of the inflammatory response.

Complete trisomy is a fatal chromosomal anomaly commonly associated with multiple phenotypic abnormalities. The associated hematologic abnormalities that occur with this disorder are not as well known, however. We present a case of a live-born female infant with this anomaly and discuss in detail the hematologic features of the peripheral blood. Abnormal physical features of the infant and the placenta are also discussed.

Neutrophil specific granule deficiency (SGD) is a congenital disorder associated with an impaired inflammatory response and a deficiency of several granule proteins. The underlying abnormality causing the deficiencies is unknown. We examined mRNA transcription and protein synthesis of two neutrophil granule proteins, lactoferrin and myeloperoxidase in SGD. Metabolically labeled SGD nucleated marrow cells produced normal amounts of myeloperoxidase, but there was no detectable synthesis of lactoferrin. Transcripts of the expected size for lactoferrin were detectable in the nucleated marrow cells of two SGD patients, but were markedly diminished in abundance when compared with normal nucleated marrow cell RNA. Because lactoferrin is secreted by the glandular epithelia of several tissues, we also assessed lactoferrin in the nasal secretions of one SGD patient by ELISA and immunoblotting. Nasal secretory lactoferrin was the same molecular weight as neutrophil lactoferrin and was secreted in normal amounts. From these data, we conclude that lactoferrin deficiency in SGD neutrophils is tissue specific and is secondary to an abnormality of RNA production. We speculate that the deficiency of several granule proteins is due to a common defect in regulation of transcription that is responsible for the abnormal myeloid differentiation seen in SGD patients.

2 members of a family, a child and his father, showed a combined morphological abnormality of leukocytes and platelets. The abnormality consisted of the presence of pseudodrumsticks in the neutrophils and of large platelets. One or more than one pseudodrumstick was present in about 40% of neutrophils. Leukocyte count, differential count and enzymatic stains were normal. Large platelets constituted about 25% of the platelet population. 1 patient also had mild thrombocytopenia which appeared to be unrelated to the basic defect since it appeared after a parotitis infection. Platelet function was normal but for a moderate prolongation of the bleeding time in the patient who had mild thrombocytopenia. No chromosomal abnormality was present in the propositi. The condition seems different from other leukocyte and platelet abnormalities so far described.

Hematological and histological studies of the rabbit brachydactyly mutant were made to clarify the question of the blood abnormality that had previously been implicated in the teratogenic process leading to congenital amputation. The hemoglobin of fetal and adult br/br rabbits, studied by electrophoresis and cyanmethemoglobin assay, exhibited no differences from that of controls. The br/br fetuses were polycythemic and severely macrocytic. Fetal limb vessels showed thrombosis leading to hemorrhages in the extremities. The hepatic tissue was abnormal, being particularly poor in hematopoietic cells; blood cell macrocytosis was attributed to impaired erthropoiesis. Treatment of pregnant rabbits with folic acid plus vitamin B12 or with folinic acid was able simultaneously to prevent the fetal blood cell macrocytosis and the congenital abnormalities.