Diagnosis and clinical management of red cell membrane disorders

Heterogeneous red blood cell (RBC) membrane disorders and hydration defects often present with the common clinical findings of hemolytic anemia, but they may require substantially different management, based on their pathophysiology. An accurate and timely diagnosis is essential to avoid inappropriate interventions and prevent complications. Advances in genetic testing availability within the last decade, combined with extensive foundational knowledge on RBC membrane structure and function, now facilitate the correct diagnosis in patients with a variety of hereditary hemolytic anemias (HHAs). Studies in patient cohorts with well-defined genetic diagnoses have revealed complications such as iron overload in hereditary xerocytosis, which is amenable to monitoring, prevention, and treatment, and demonstrated that splenectomy is not always an effective or safe treatment for any patient with HHA. However, a multitude of variants of unknown clinical significance have been discovered by genetic evaluation, requiring interpretation by thorough phenotypic assessment in clinical and/or research laboratories. Here we discuss genotype-phenotype correlations and corresponding clinical management in patients with RBC membranopathies and propose an algorithm for the laboratory workup of patients presenting with symptoms and signs of hemolytic anemia, with a clinical case that exemplifies such a workup.

Complex Modes of Inheritance in Hereditary Red Blood Cell Disorders: A Case Series Study of 155 Patients

Hereditary erythrocytes disorders include a large group of conditions with heterogeneous molecular bases and phenotypes. We analyzed here a case series of 155 consecutive patients with clinical suspicion of hereditary erythrocyte defects referred to the Medical Genetics Unit from 2018 to 2020. All of the cases followed a diagnostic workflow based on a targeted next-generation sequencing panel of 86 genes causative of hereditary red blood cell defects. We obtained an overall diagnostic yield of 84% of the tested patients. Monogenic inheritance was seen for 69% (107/155), and multi-locus inheritance for 15% (23/155). PIEZO1 and SPTA1 were the most mutated loci. Accordingly, 16/23 patients with multi-locus inheritance showed dual molecular diagnosis of dehydrated hereditary stomatocytosis/xerocytosis and hereditary spherocytosis. These dual inheritance cases were fully characterized and were clinically indistinguishable from patients with hereditary spherocytosis. Additionally, their ektacytometry curves highlighted alterations of dual inheritance patients compared to both dehydrated hereditary stomatocytosis and hereditary spherocytosis. Our findings expand the genotypic spectrum of red blood cell disorders and indicate that multi-locus inheritance should be considered for analysis and counseling of these patients. Of note, the genetic testing was crucial for diagnosis of patients with a complex mode of inheritance.

Human ankyrins and their contribution to disease biology: An update

Ankyrins (Ank)are ubiquitously expressed proteins that play a critical role in the integrity of cytoskeleton and cellular signalling. Their presence in metazoans and evolutionary conserved protein primary sequence indicates their functional significance. Tissue-specific isoforms and an array of transcript variants make this protein one of the indispensable cellular components. Membrane-binding domains consist of ankyrin repeats that bind with several functional membrane proteins that enable maintaining cellular integrity. Cytosolic ankyrins help in cellular signal transduction. Linkage studies and recent genome-wide association studies uncovered the pathogenic roles of ankyrins (ankyrin-R, ankyrin-B and ankyrin-G) in several diseases, such as hereditary spherocytosis, long QT syndrome, intellectual disability, and CRASH syndrome, among several others. Identification of Ank3 in celiac disease may potentially explain the link between neuronal health and immunity. It is thus warranted to investigate the role of neuronal factors in immune diseases and vice versa. In this review, we briefly discussed the contribution of ankyrin genes to human diseases.

Inherited hemolytic anemia: a possessive beginner's guide

Significant advances have been made in diagnosis and clinical management of inherited red cell membrane disorders that result in hemolytic anemia. Membrane structural defects lead to hereditary spherocytosis (HS) and hereditary elliptocytosis (HE), whereas altered membrane transport function accounts for hereditary xerocytosis (HX) and hereditary overhydrated stomatocytosis (OHS). The degrees of membrane loss and resultant increases in cell sphericity determine the severity of anemia in HS and HE, and splenectomy leads to amelioration of anemia by increasing the circulatory red cell life span. Alterations in cell volume as a result of disordered membrane cation permeability account for reduced life span red cells in HX and OHS. Importantly, splenectomy is not beneficial in these 2 membrane transport disorders and is not recommended because it is ineffective and may lead to an increased risk of life-threatening thrombosis. Rational approaches are now available for the diagnosis and management of these inherited red cell disorders, and these will be discussed in this review.

Mechanics of diseased red blood cells in human spleen and consequences for hereditary blood disorders

In red blood cell (RBC) diseases, the spleen contributes to anemia by clearing the damaged RBCs, but its unique ability to mechanically challenge RBCs also poses the risk of inducing other pathogenic effects. We have analyzed RBCs in hereditary spherocytosis (HS) and hereditary elliptocytosis (HE), two typical examples of blood disorders that result in membrane protein defects in RBCs. We use a two-component protein-scale RBC model to simulate the traversal of the interendothelial slit (IES) in the human spleen, a stringent biomechanical challenge on healthy and diseased RBCs that cannot be directly observed in vivo. In HS, our results confirm that the RBC loses surface due to weakened cohesion between the lipid bilayer and the cytoskeleton and reveal that surface loss may result from vesiculation of the RBC as it crosses IES. In HE, traversing IES induces sustained elongation of the RBC with impaired elasticity and fragmentation in severe disease. Our simulations thus suggest that in inherited RBC disorders, the spleen not only filters out pathological RBCs but also directly contributes to RBC alterations. These results provide a mechanistic rationale for different clinical outcomes documented following splenectomy in HS patients with spectrin-deficient and ankyrin-deficient RBCs and offer insights into the pathogenic role of human spleen in RBC diseases.

Mean reticulocyte volume: a specific parameter to screen for hereditary spherocytosis

This study assessed the value of mean reticulocyte volume (MRV) for differential diagnosis of hereditary spherocytosis (HS) so as to develop conventional and new specific screen indexes. Subjects in this study were divided into three groups: 53 cases in HS group, 217 cases in hemolytic anemia control group (109 cases of thalassemia (THAL), 56 cases of glucose-6-phosphate dehydrogenase G6PD deficiency anemia, and 52 cases of autoimmune hemolytic anemia (AIHA)), and 100 cases in healthy control group. We analyzed erythrocyte and reticulocyte parameters including MRV, mean sphered corpuscular volume, mean corpuscular hemoglobin concentration, and immature reticulocyte fraction. Results demonstrated that MRV was significantly lower in the HS group but significantly higher in the AIHA and G6PD deficiency anemia groups than that in the healthy control group (P = 0.000). MRV was not significantly different between the AIHA and G6PD deficiency anemia groups (P = 0.977) and between the healthy control and THAL groups (P = 0.168). The area under the ROC curve of MRV for diagnosis of HS was 0.942, with a standard error of 0.019, 95% confidence interval of 0.905-0.979, and optimal critical diagnosis point of 95.77 fL. When the MRV was ≤95.77 fL, the sensitivity and specificity for diagnosis of HS were 86.80% and 91.20%, respectively. Therefore, MRV is a general and specific new index for screening HS and important for differential diagnosis of different types of hemolytic anemia.

Evaluation of a Flow-Cytometric Osmotic Fragility Test for Hereditary Spherocytosis in Chinese Patients

BACKGROUND

Osmotic fragility testing based on flow cytometry was recently introduced for the screening of hereditary spherocytosis (HS). This study was undertaken to evaluate the clinical diagnostic value of a flow-cytometric osmotic fragility test for HS.

METHODS

Peripheral blood was collected from 237 subjects at the First Affiliated Hospital of Guangxi Medical University, including 56 HS patients, 86 thalassemia patients and 95 healthy controls. The samples were examined by flow-cytometric osmotic fragility test and the percentage of residual red blood cells was used to determine HS. Peripheral blood smears were performed to examine the red blood cell morphology.

RESULTS

With clinical diagnosis of HS as the gold standard and the percentage of residual red blood cells <23.6% as the diagnostic threshold in the flow-cytometric osmotic fragility test, the sensitivity of the flow-cytometric osmotic fragility test for HS was 85.71% and the specificity was 97.24%.

CONCLUSION

The flow-cytometric osmotic fragility test combined with a red blood cell morphology test by peripheral blood smear could be a simple, practical and accurate laboratory screening method for HS.

Erythropoiesis versus inflammation in Hereditary Spherocytosis clinical outcome

OBJECTIVES

This study aimed to evaluate the relationship between erythropoiesis and inflammation, in Hereditary Spherocytosis (HS) clinical outcome.

DESIGN AND METHODS

We studied 26 controls and 82 HS patients presenting mild (n = 49) and severer (n = 33) HS forms. We evaluated plasma levels of EPO, sTfR, ferritin, iron, folic acid, vitamin B12, TNF-α, IFN-γ, elastase and lactoferrin; leukocyte and reticulocyte counts and RPI were determined.

RESULTS

All HS patients showed significantly higher EPO, sTfR, reticulocytes and RPI but only mild HS presented normal hemoglobin levels; the positive significant correlations between EPO and sTfR, reticulocytes and RPI observed in mild HS were not observed in severer HS patients. HS patients presented with higher levels of neutrophils, TNF-α, IFN-γ, elastase, lactoferrin and ferritin.

CONCLUSIONS

Our data show HS as a disease linked to enhanced erythropoiesis that is disturbed in the more severe forms, to which inflammation may contribute, at least in part.

Aplastic crisis induced by human parvovirus B19 as an initial presentation of hereditary spherocytosis

The association between aplastic crisis and human parvovirus (HPV) B19 infection has been described in patients with hereditary spherocytosis (HS). Most cases of aplastic crisis in patients with HS induced by HPV B19 have been reported in children and adolescents. In this paper, we describe an aplastic crisis induced by HPV B19 in the 34 year old female as an initial presentation of HS. Although other viral illnesses cause some decompensation in HS, the anemia is rarely as profound as seen in acute HPV B19 infections.

[Hereditary spherocytic hemolytic anemia in an adult with the formation of ectopic foci of extramedullary hemopoiesis in the chest]

The paper describes a rare case of formation of paravertebral extramedullary hemopoietic foci in microspherocytic anemia or Minkovsky-Shoffar disease in an adult. Therapeutic splenectomy has led to regression of extramedullary hemopoietic foci, which supports that there is a direct relationship of the above formations to the specific features of the etiology and pathogenesis of microspherocytic anemia.

Stuttering priapism associated with hereditary spherocytosis

Stuttering priapism is a clinical phenomenon that occurs commonly in certain patient populations, including sickle cell anemia and other hematologic dyscrasias. Although the mechanism is still not completely understood, treatment is focused on prevention of recurrence in the outpatient setting, and immediate detumescence and minimizing corporal fibrosis in the acute setting. We present a case of stuttering priapism in a 44 year-old male with hereditary spherocytosis and discuss the pathophysiology and clinical management of this entity.

Splenic infarction after Epstein-Barr virus infection in a patient with hereditary spherocytosis

We describe the first patient with hereditary spherocytosis (HS) known to have developed splenic infarction following infectious mononucleosis (IM). An 18-year-old Japanese man was referred to our hospital in November 2004 because of continuous fever and icterus. He had undergone cholecystectomy at the age of 14 years. On patient admission in November 2004, a physical examination showed marked hepatosplenomegaly, icterus, and jaundice. He had a white blood cell count of 14.9 x 10(9)/L with 9.5% atypical lymphocytes, a red blood cell count of 2.93 x 10(12)/L, and a hemoglobin concentration of 7.8 g/dL. Microspherocytes were observed in the patient's peripheral blood smear, and immunoglobulin M antibody to Epstein-Barr virus (EBV) viral capsid antigen was detected. The patient's diagnosis was HS with IM. On day 4 of admission, the patient complained of severe abdominal pain. Abdominal computed tomography scanning revealed findings of splenic infarction. Two months after the occurrence of splenic infarction, a splenectomy was performed. A pathohistologic examination of the resected spleen revealed no evidence of thrombosis or arterial occlusion. We assume that the cause of splenic infarction was insufficient blood flow to oxygenate the entire spleen during the acute enlargement of the spleen.

Physiologically important secondary modifications of red cell membrane in hereditary spherocytosis-evidence for in vivo oxidation and lipid rafts protein variations

Hereditary spherocytosis (HS) is a heterogeneous group of disorders. The abnormal red cell morphology (resulting in shortened cell survival) is due to a primary deficiency in spectrin, ankyrin-1, band 3 or protein 4.2. Secondary protein deficiencies are often observed and may be involved in the outcome of the disease. In the present study, we searched for secondary erythrocyte membrane protein alterations in HS, including the lipid raft associated proteins and the oxidative index. For this purpose, 12 patients with clinical and laboratory diagnosis of mild to typical HS were examined. Erythrocyte membrane ghosts and skeletons were subjected to SDS-PAGE and immunoblotting analysis using antibodies against red cell membrane proteins and DNP moiety, after 2,4-dinitrophenylhydrazine derivatization. Protein deficiencies, degradation, aggregation and enhanced binding of cytoplasmic components, band 8, hemoglobin and immunoglobulins G to the membrane as well as increased oxidative index, were found in the majority of the HS patients. Proportion of the membrane- and skeleton-bound globin was oxidized/denatured Hb or hemichromes and crosslinkings. Some HS membranes are deficient in lipid rafts proteins and contain sorcin. A context of these distortions is more pronounced in typical HS cases compared to the mild ones. Similar defects in thalassemia and senescent RBCs are dictated by increased oxidative stress and are positively correlated with perturbations in membrane properties. These data add some new insight in the field of HS pathophysiology and clinical variability.

Abnormality of CD4(+)CD25(+) regulatory T cells in idiopathic thrombocytopenic purpura

OBJECTIVES

The aim of this study was to explore the profile and function of CD4(+)CD25(+) regulatory T cells (Treg cells) in idiopathic thrombocytopenic purpura (ITP) patients.

METHODS

Treg cell numbers were analyzed by flow cytometric analysis in peripheral blood mononuclear cells collected from healthy donors or patients with ITP. Quantification of cell proliferation was assayed by an enzyme-linked immunosorbent assay kit, based on the measurement of BrdU incorporation during DNA synthesis.

RESULTS

The percentage of Treg cells was significantly decreased in ITP patients in active and non-remission state(5.79 +/- 1.22%) when compared with the patients in remission(11.63 +/- 4.56%) and to healthy subjects(12.68 +/- 3.59%). The suppressive activity of Treg cells in ITP patients was also found to be impaired.

CONCLUSION

These results suggest that decreased number and function of Treg cells might be one of mechanisms that cause immune regulation dysfunction in ITP.

Lumenal localization in the endoplasmic reticulum of the C-terminal tail of an AE1 mutant responsible for hereditary spherocytosis in cattle

An R664X nonsense mutant AE1 is responsible for dominant hereditary spherocytosis in cattle and is degraded by the proteasomal endoplasmic reticulum-associated degradation. The present study demonstrated that R664X AE1 translated in vitro had the trypsin-sensitve site identical to that of the wild-type AE1. The P661S/R664X mutant containing a possible N-glycosylation site at Asn660 showed an increase in size by 3 kDa both in the cell-free translation system and in transfected HEK293 cells. Moreover, steady state levels of R664X and P661S/R664X in HEK293 cells were markedly increased in the presence of a proteasome inhibitior. These findings indicate that the truncated C-terminal region of R664X AE1 has lumenal localization in the endoplasmic reticulum and is not accessible to proteasomal machineries in the cytosol.

Near-total splenectomy for hereditary spherocytosis: clinical prospects in relation to disease severity

We prospectively studied the efficacy of near total splenectomy (NTS) for managing hereditary spherocytosis (HS) based on haemoglobin (Hb), total bilirubin and splenic remnant regrowth in 30 children receiving NTS for HS between November 1996 and December 2004 (mean followup 3.6 years). Patients were classified into three severity groups. At followup, mean Hb had increased by 2.9-5.0 g/dl (P = 0.110) and bilirubin dropped by 15.4-56.4 mumol/l. Remnant regrowth was moderate, within the weight-specific norm. Amongst spleen-preserving techniques, NTS shows markedly lower rates of recurrent haemolysis, remnant regrowth and secondary operations, thus potentially benefiting all clinical forms of HS.

Prosthetic heart valves’ mechanical loading of red blood cells in patients with hereditary membrane defects

Implantable cardiovascular devices such as prosthetic heart valves (PHVs) are widely applied clinical tools. Upon implantation, the patient can suffer from anemia as a result of red cell destruction and hemolysis can be more relevant whenever the patient is also affected by red cell disorders in which erythrocytes are more susceptible to mechanical stress such as hereditary spherocytosis (HS) and hereditary elliptocytosis (HE). Considering the typical morphological alterations observed in HS and HE, a study of the influence of cell geometry on the distribution of the shear stress on red cells in biological fluids was carried out. A numerical simulation of the loading caused by Reynolds shear stresses on a prolate spheroid was performed, with the ellipticity of the particle as the independent parameter. The average shear stress on a particle in the blood stream was found to depend on the particle's geometry, besides the stress field produced by the prosthetic device. The relevance of an increasing particle ellipticity on the global load is discussed. The model was applied to erythrocytes from implanted patients with HE or HS, enabling to explain the occurrence of moderate or severe anemia, respectively. The clinical data support the relevance of the proposed global parameter as erythrocyte trauma predictor with regard to the fluid dynamics of artificial organs.

Asymptomatic spherocytosis presenting with spinal cord compression

✓ Extramedullary hematopoiesis (EMH) is a compensatory mechanism occurring in patients with chronic anemia, which occurs most frequently with thalassemia. The authors report the case of a 57-year-old man, with no history of clinical or hematological disease, presenting with spinal cord compression. Magnetic resonance (MR) imaging demonstrated a homogeneous posterior epidural mass extending from T-3 to T-6. Following decompressive surgery, the patient's symptoms improved. Histological analysis showed features consistent with a diagnosis of EMH. Subsequent workup was remarkable for an asymptomatic spherocytosis without anemia. There was no family history of anemia. An EMH-related presentation of mild spherocytosis has been described in the literature, but its epidural location led to spinal cord compression. The MR imaging features were suggestive of EMH, but in the presence of spinal cord compression and in the absence of a history of chronic anemia, the authors did not believe that nonsurgical management would have been reasonable.

Recurrent hemolysis-associated pseudoerysipelas of the lower legs in a patient with congenital spherocytosis

A 29-year-old patient presented with recurrent erythematous eruptions on both lower legs of 15 years' duration. Family history, along with clinical and laboratory examinations, revealed congenital hereditary spherocytosis and excluded other reasons for the erythematous eruptions of the lower legs. During two subsequent episodes, we detected increased hemolysis that disappeared concomittantly on spontanous resolution of the lesions. To our knowledge, this case is the first report showing a recurrent erythematous eruption on the lower legs in a patient with congenital hereditary spherocytosis. These eruptions might be caused by intermittent hemolysis-induced inflammation as a result of the increased osmotic fragility of the erythrocytes and may evolve to chronic leg ulcers later in life.

Experience with eosin-5'-maleimide as a diagnostic tool for red cell membrane cytoskeleton disorders

The diagnosis of hereditary spherocytosis (HS) is based on red cell morphology and other conventional tests such as osmotic fragility, autohemolysis and acidified glycerol lysis. However, milder cases are at times difficult to diagnose. Confirmation by red blood cell (RBC) membrane protein analysis is not possible in most laboratories. Recently, a flow cytometric method has been described for quantitating the fluorescence intensity of intact red cells after incubation with the dye eosin-5'-maleimide (EMA), which binds specifically to the anion transport protein (band-3) at lysine-430. This has been shown to be an effective screening test for red cell membrane disorders. We evaluated the usefulness of this approach for screening membrane protein disorders such as HS and hereditary elliptocytosis (HE) and its value in discriminating this group from other hemolytic anemias, such as glucose-6-phosphate dehydrogenase (G6PD) deficiency, beta-thalassemia trait, sickle cell anemia and autoimmune hemolytic anemia. Fluorescence intensity, expressed in mean channel fluorescence (MCF) units, was determined using a Becton Dickinson FACS Caliber flow cytometer. Membrane protein analysis was carried out by sodium dodecyl sulfate-polyacrylamide gel eletrophoresis (SDS-PAGE). RBCs from patients with HS and HE gave significantly lower MCF values (P < 0.001) than the normal control group and other patient groups. The diagnosis of HS in four cases was confirmed by RBC membrane protein electrophoresis and all showed a deficiency of spectrin. The advantage of the EMA dye method are its specificity for membrane disorders, as well as being a simple, user-friendly and rapid method which is inexpensive, provided a flow cytometer is available.

Demonstration and quantification of "hyperchromic" erythrocytes by haematological analysers. Application to screening for hereditary and acquired spherocytosis

The double laser beam diffraction of spherized RBC used in the ADVIA 120 haematological analyser allows quantitation of cells aberrant not only by their volume but also by their haemoglobin concentration. The present investigation provides arguments for the identification of hyperchromic RBC as spherocytes, mainly the close relation between % hyperchromic cells and % lysed by the cryohaemolysis test. The percentage of hyperchromic erythrocytes may no longer be considered an instrumental artefact. Without allowing a definite diagnosis of hereditary spherocytosis, an increased percentage of hyperchromic cells indicates the degree of spherocytosis, making it an excellent automated and cost-free screening parameter for inherited and acquired corpuscular haemolysis.

Pelvic extramedullary haematopoiesis associated with hereditary spherocytosis

Extramedullary haematopoiesis (EMH) is a rare disorder and is characterised by the appearance of haemopoietic tissue outside of the bone marrow. The most common of the previously recognised sites of EMH are the spleen and the liver. This case-report describes a unique case of pelvic EMH secondary to herditary spherocytosis with regression of the lesion following splenectomy. Current principles of managing EMH are also discussed.

Extramedullary paraspinal hematopoiesis in hereditary spherocytosis

Extramedullary hematopoiesis is a rare condition, characterized by the appearance of hematopoietic elements outside the bone marrow. It occurs primarily in patients with chronic myeloproliferative disorder or congenital hemolytic anemia. We report on a 60-year-old man with hereditary spherocytosis who presented with an extramedullary paraspinal hematopoietic mass, splenomegaly, and bone marrow expansion in the right distal femur and proximal tibia metaphysis. The diagnosis was established after biopsy of the paravertebral mass. The patient underwent a splenectomy.

Kallmann syndrome in a patient with congenital spherocytosis and an interstitial 8p11.2 deletion

We describe the hitherto smallest interstitial 8p11.2 deletion in a patient with congenital spherocytosis, dysmorphic features, and growth delay in association with hypogonadotropic hypogonadism and anosmia. The latter features are characteristic for Kallmann syndrome. In contrast to the previously reported patients with 8p deletions, the present patient showed normal intelligence. Congenital spherocytosis is one of the most common hereditary hemolytic anemias. One of the three loci for congenital spherocytosis was assigned to chromosome 8p (located between 8p11.1 and 8p21) and mutations in or loss of the ankyrin-1 gene (ANK1) were identified. Molecular analysis confirmed the de novo loss of ANK1 in our patient. Kallmann syndrome, which is characterized by hypogonadotropic hypogonadism and anosmia, can be X-linked, autosomal dominant, or autosomal recessive. So far only the X-linked KAL1 gene has been identified. The present finding suggests an autosomal locus for Kallmann syndrome at 8p11.2. The simultaneous occurrence of congenital spherocytosis, Kallmann syndrome phenotype, dysmorphic features, and growth delay in this patient points to a new contiguous gene syndrome.

Hereditary spherocytosis and hemochromatosis

A 37-year-old male, splenectomized at the age of 1 year, was admitted to the ward with severe chest pain and signs of cardiogenic shock. Clinical investigations revealed the presence of both hemochromatosis and hereditary spherocytosis (HS). HLA typing showed A3,B7 and A24,B57 haplotypes and genetic analysis revealed homozygosity for the C282Y mutation. A family study was performed. The parents and four brothers were heterozygous for the C282Y mutation. Two of the brothers also presented high levels of iron stores and they had been splenectomized because of HS, while two other siblings had neither spherocytosis nor hemochromatosis. The mother had a mild anemia with dehydrated red blood cells (RBC), while the father appeared to have low-density, but normal RBC; none of them presented with spherocytosis. All siblings with spherocytosis and elevated iron stores showed a RBC density distribution similar to the mother. We present the first case with genetically proven hemochromatosis in combination with spherocytosis, focusing on the various possibilities of iron accumulation in individuals with spherocytosis and heterozygosity for the C282Y mutation.

Band 3 anion exchanger and its involvement in erythrocyte and kidney disorders

Recent developments in the structure of erythrocyte band 3 and its role in hereditary spherocytosis and distal renal tubular acidosis are described. The crystal structure of the N-terminal cytoplasmic domain provides a basis for understanding the organization of ankyrin and other peripheral membrane proteins around band 3. Band 3 also binds integral membrane proteins, including the Rh protein complex and CD47. Band 4.2 is important in these associations, which link the Rh complex to the skeleton. It is suggested that band 3 forms the scaffold for a protein assembly that could transduce signals from the cell exterior and modulate the transport and mechanical properties of the erythrocyte. The involvement of band 3 in distal renal tubular acidosis is reviewed. The article discusses a likely mechanism for dominant distal renal tubular acidosis in which associations between the normal and mutant protein alter the plasma membrane targeting of the normal protein in the kidney.

Arterial elastorrhexis in beta-thalassaemia intermedia, sickle cell thalassaemia and hereditary spherocytosis

Arterial and stromal elastorrhexis, an elastic tissue disorder, was recently described in beta-thalassaemia major. Histopathological material from 10 patients with thalassaemia intermedia, 14 with sickle cell thalassaemia and 18 with hereditary spherocytosis was examined in order to investigate the specificity of the arteriopathy. Histological re-examination was made in a total of 42 spleens with parasplenic lymph nodes in 14 cases, 26 surgical liver biopsies and 16 gallbladders with associated regional lymph nodes. Arteriopathy, qualitatively similar to that seen in beta-thalassaemia major, was found in up to 90% of extrasplenic muscular arteries. Elastorrhexis lesions were also found in intrasplenic arteries and in stromal elastic tissue of spleens and parasplenic lymph nodes, in the absence of tissue iron overload. The arteriopathy appears in the first decade of life even in spleens of normal weight, and seems unrelated to the severity of permanent anaemia. It is suggested that patients suffering from hereditary chronic haemolytic diseases are subject to an elastic tissue disorder which is similar to hereditary pseudoxanthoma elasticum, the earliest and most frequent manifestation of which is arterial elastorrhexis of muscular extrasplenic arteries.

Amphiphile-induced vesiculation in aged hereditary spherocytosis erythrocytes indicates normal membrane stability properties under non-starving conditions

Aged HS erythrocytes with a defined primary defect in band 3 protein or ankyrin were incubated with amphiphiles (detergents) at sublytic concentrations (37 C, 60 min) or glucose-starved (37 C, 24 h). In line with previous studies, the release of AChE (exovesicles) from HS erythrocytes during glucose-starvation was significantly higher (11%) compared to that from control erythrocytes (1%). Control and HS cells responded, however, similarly to amphiphile-treatment (non-starving conditions). Amphiphiles induced similar types of shape alterations and a similar amount of AChE release (14-15%). Furthermore, the size and shape of amphiphile-induced exo- and endovesicles released from control and HS erythrocytes were similar. The results suggest that the stability properties of the membrane are not seriously disturbed in aged HS erythrocytes under non-starving conditions.

Reduced incidence of thrombosis in mice with hereditary spherocytosis following neonatal treatment with normal hematopoietic cells

Thrombosis is a life-threatening complication of hemolytic anemia in humans. Cardiac thrombi are present in all adult alpha-spectrin-deficient (sph/sph) mice with severe hereditary spherocytosis, providing a model for events preceding thrombosis. The current study evaluated (1) the timing of thrombosis initiation and (2) the effect of postnatal transplantation of normal cells on life span and thrombotic incidence in adult mice. Thrombi are detected histologically following necropsy in untreated sph/sph mice of various ages and are not observed until 6 weeks of age. Thrombotic incidence increases from 50% at 6 to 7 weeks of age to 100% at 9 weeks of age. As a potential therapy, nonablated sph/sph neonates were transfused with either genetically marked normal peripheral blood (PB), bone marrow (BM), or both and assessed for donor cells and thrombosis. A single transfusion of PB, with or without BM, significantly increases the percentage of sph/sph mice that survive to weaning (4 weeks of age). Replacement in all sph/sph recipients is limited to red blood cells (RBCs). RBCs derived from donor PB are lost within 5 weeks. PB plus BM prolongs high-level donor PB cell production better than BM alone. Thrombotic incidence is significantly reduced in all sph/sph mice treated with PB, BM, or both. Hence, the presence of normal blood cells in the peripheral circulation of neonatal and adult sph/sph mice rescues the former and abrogates the development of thrombosis in the latter. (Blood. 2001;97:3972-3975)

Increase in band 3 density and aggregation in hereditary spherocytosis

PURPOSE

Red cells in hereditary spherocytosis are characterized by a reduced surface area/volume ratio. The mechanisms leading to the loss of membrane material and subsequent elimination of the cells have still not been clarified. It was the aim of the present study to analyze band 3 distribution in the red cell membrane and its putative role in red cell elimination.

METHODS/RESULTS

Immunogold histochemistry was performed to detect band 3 in red cell membranes. Band 3 density and distribution were visualized by electron microscopy. Unsplenectomized spherocytosis patients (n = 12) showed reduced band 3 density and aggregation compared to controls (n = 15) (density: 1.2 +/- 0.1 gold particles/microm circumference of red cell membrane vs 1.5 +/- 0.07 gold particles/microm, x +/- SEM; P < 0.05; aggregation: 0.26 +/- 0.02 aggregates/microm vs 0.3 +/- 0.02 aggregates/microm). By contrast, band 3 density and aggregation were increased in spherocytosis patients who had undergone splenectomy (density: 2.8 +/- 0.1 gold particles/microm vs 2.0 +/- 0.1 gold particles/microm; P < 0.05; aggregation: 1.5 +/- 0.1 aggregates/microm vs 0.5 +/- 0.03 aggregates/microm; P < 0.01). Artificial ageing of red cells from healthy controls (n = 6) led to a significant increase in band 3 aggregation (2.06 +/- 0.2 aggregates/microm vs 0.33 +/- 0.1 aggregates/microm; P(Wilcoxon) < 0.01) but no change in band 3 density. In hereditary spherocytosis (n = 6), both band 3 density and aggregation increased significantly after artificial ageing of the red cells. The elevated band 3 aggregation was associated with a stimulated erythrophagocytosis in vitro.

CONCLUSION

Band 3 aggregation characterizes the red cells in hereditary spherocytosis. It may be the cause of selective splenic phagocytosis of both spherocytes and senescent erythrocytes.

Amelioration of severe hereditary spherocytosis in nonablated adult mice by marrow transplantation

Human severe hereditary spherocytosis (sHS) is life threatening and transfusion dependent. sHS is lethal within 6 days of birth for 99% of jaundiced (ja/ja) mice, making these mice excellent models for early therapeutic interventions. Nonablated ja/ja neonates simultaneously transfused and given intravenous injections of normal marrow become chimeric for donor cells. Significant improvement of red blood cell parameters occurs but is temporary because the donor marrow-derived cells gradually disappear from the circulation. The average lifespan, however, is increased to 8.7 months. We postulate that donor cells are diluted by rapidly proliferating host cells during postnatal growth. Here, we test this hypothesis by determining whether treatment of adults improves long-term therapy. Nonablated ja/ja adults rescued by a single neonatal transfusion were injected intravenously with 1 x 10(10) normal, genetically marked donor marrow cells/kg body weight. Donor cell implantation and blood parameters were monitored periodically and tissue histopathology was determined at necropsy.sHS recipients with 100% donor erythroid cells have significantly improved red blood cell counts throughout life when compared with ja/ja controls transfused once at birth. Total serum iron and bilirubin levels are corrected in ja/ja marrow recipients. Donor-implanted HS mice necropsied at 16 to 21 months of age have normal mean cell hemoglobin concentration and dramatically decreased tissue iron deposits. Reticulocyte counts but not red cell counts normalize, suggesting the HS mice reset their response to hypoxia. Nonablative transplantation performed after cessation of host postnatal red blood cell amplification can be therapeutic long term for transfusion-dependent hemolytic anemias.

Hereditary spherocytosis and elliptocytosis erythrocytes show a normal transbilayer phospholipid distribution

Phosphatidylserine (PS) asymmetry was determined in red blood cells from patients with hereditary spherocytosis and elliptocytosis. No PS-exposing subpopulations were detected using the very sensitive method with fluorescently labeled annexin V. Treatment with N-ethylmaleimide or adenosine triphosphate (ATP) depletion to inactivate the flipase did not lead to formation of PS-exposing subpopulations in these cells, but elevated intracellular calcium levels did lead to extensive scrambling of the PS asymmetry. Although interactions of the membrane skeleton with the phospholipid bilayer have been suggested to stabilize the asymmetric distribution of PS across the bilayer, our data show that red blood cells with a severely damaged membrane skeleton are able to preserve asymmetry, even under conditions in which restoration of the asymmetric distribution is excluded. Moreover, the loss of membrane asymmetry in these cells requires active scrambling involving high levels of intracellular calcium as in normal cells. Our data show that the severe disorder of the membrane skeleton found in these cells does not affect the activity of flipase or scramblase, indicating that these proteins are not regulated by, nor coupled to the membrane skeleton assembly, and that possible thrombotic events in spherocytosis patients are not likely associated with altered PS topology of the red blood cells.

Homozygous missense mutation (band 3 Fukuoka: G130R): a mild form of hereditary spherocytosis with near-normal band 3 content and minimal changes of membrane ultrastructure despite moderate protein 4.2 deficiency

The characteristics of phenotypic expression were studied in a Japanese family with hereditary spherocytosis and an extremely rare homozygous missense mutation of the band 3 gene (band 3 Fukuoka: G130R). The homozygous unsplenectomized proband was a 29-year-old male with compensated haemolytic anaemia (red cell count 4.21 x 10(12)/l, reticulocytes 278 x 10(9)/l, and indirect bilirubin 44 micromol/l). His red cell band 3 (B3) protein demonstrated a 9.3% reduction and his protein 4.2 (P4.2) level was substantially reduced (45.0%), compared to normal subjects. P4.2 protein was composed mostly of a wild type (72 kD) with a trace of 68 kD peptide. The binding properties of the mutated B3 to normal P4.2 were significantly impaired, which probably resulted in the substantial reduction of P4.2 in this proband, since no abnormalities were detected on the P4.2 gene. Electron microscopy (EM) using the freeze-fracture method demonstrated a mild decrease in intramembrane particles (IMPs) of near-normal size (8 nm in diameter) with no substantial increases in their oligomerization. Their distribution on the membrane P face was almost normal, although most of the IMPs could represent the homozygously mutated B3 protein. EM (quick-freeze deep-etching method) disclosed a skeletal network of near-normal size and size distribution of the skeletal units, suggesting that the mutated B3 protein itself did not have much effect on the skeletal network in situ. Therefore the reduced P4.2 content (45% of that of normal subjects), which remained on the red cell membrane of this proband, appeared to be nearly sufficient for maintaining the normal structure of the skeletal network and IMPs in situ, contrary to the marked abnormalities in both IMPs and the skeletal network in complete P4.2 deficiencies.

Thrombosis and secondary hemochromatosis play major roles in the pathogenesis of jaundiced and spherocytic mice, murine models for hereditary spherocytosis

Jaundiced mice, ja/ja, suffer from a severe hemolytic anemia caused by a complete deficiency of erythroid beta-spectrin. We used these mice as a model to investigate the pathophysiological consequences of the deficiency, including the effects in the nonerythroid tissues where this protein is expressed. Because the ja/ja mice rarely survive beyond the fourth postnatal day, methods were assessed for extending lifespan into adulthood. Neonatal transfusion increased lifespan to a mean of 3.7 months, allowing a more complete characterization of the pathophysiology. Blood parameters and histopathology of the jaundiced mouse were compared with that from spherocytic mice, which have a hemolytic anemia caused by deficiency of erythroid alpha-spectrin, yet can survive the postnatal period transfusion free. The adult jaundiced and spherocytic mice present with greatly decreased hematocrit and red blood cell counts, reticulocytosis, and bilirubinemia, leading secondarily to hepatosplenomegaly and cardiomegaly. Jaundiced and spherocytic mice were analyzed histopathologically between 1.0 and 9.5 months of age. Interestingly, the complete absence of erythroid beta-spectrin in jaundiced mice leads to no detectable structural defects in brain, cardiac, or skeletal muscles. However, fibrotic lesions and lymphocytic infiltration were observed in cardiac tissue from 4 of 13 jaundiced mice and 15 of 15 spherocytic mice, and thrombi were detected at either the atrioventricular valves or within the atria of 2 of 13 jaundiced mice and 15 of 15 spherocytic mice. In addition, all affected mice had a progressive renal hemosiderosis concurrent with hydronephrosis and glomerulonephritis. The severity of the renal disease and its presence in all moribund mice suggests kidney failure rather than the fibrotic heart lesions as the major cause of death in these mice.

Red cell abnormalities in hereditary spherocytosis: relevance to diagnosis and understanding of the variable expression of clinical severity

Marked variations in the clinical manifestations of hereditary spherocytosis (HS) have long been recognized. However, neither the molecular nor the cellular basis for this variable expression has been fully delineated. To better define the cellular basis for variable expression of the disease, we evaluated the pathobiology of red cells in a large series of 55 non-splenectomized and 31 splenectomized patients with HS. Red cell membrane surface area, surface area-to-volume ratio, cell volume, and state of cell hydration were quantitated. We found that decreased membrane surface area was a distinguishing feature of red cells in all patients studied, whereas decreased surface area-to-volume ratio as reflected by increased osmotic fragility was noted in only 66% of the non-splenectomized patients. In terms of red cell indexes, the percentage of microcytes was not a good discriminator of HS phenotype but was the best indicator of the severity of the disease. In contrast, the presence of increased numbers of hyperdense cells was an effective discriminating feature of the HS phenotype but a poor indicator of disease severity. These findings have enabled us to define the dominant cellular changes that account for the variable clinical severity of this common red cell membrane disorder and have allowed development of improved approaches for its diagnosis.

Cytoskeletal behaviour in spectrin and in band 3 deficient spherocytic red cells: evidence for differentiated splenic conditioning role

Based on quantitative analysis of red cell membrane proteins, hereditary spherocytosis (HS) can be divided into two main groups including isolated or ankyrin combined spectrin deficiency and band 3 reduction. Protein methyl esterification catalysed by protein carboxyl methyl-transferase (PCMT type II; EC 2.1.1.77) is a post-biosynthetic modification which is involved in the metabolism of damaged membrane proteins. We utilized the evaluation of erythrocyte membrane protein methyl esterification as a marker of cytoskeletal disarray in seven HS subjects with spectrin reduction and in seven patients with HS due to band 3 deficiency. Our results support the notion that band 3 deficient erythrocytes are not affected by an extensive cytoskeletal derangement. On the contrary, we found a remarkable increase of membrane methylation in the unsplenectomized, spectrin-deficient. HS patients, suggesting a striking membrane skeleton disarray. This phenomenon was not observed in the spectrin-deficient red cells of splenectomized patients. Therefore in spectrin deficient erythrocytes the induction of cytoskeletal damage, specifically recognized by PCMT type II, could be one of the splenic steps producing conditioned spherocytes.

[The spleen in hereditary spherocytosis]

Hereditary spherocytosis is the most common inherent, autosomal dominant hemolytic anemia. Mild splenomegaly, venostasis and common decrease of while pulp is characteristic for hereditary spherocytosis. Cords are filled with spherocytes, sinuses can be empty or squeezed. Both sinuses and veins include ghost erythrocytes that lost haemoglobin. They are seen light-microscopically in differential interferent contrast. Macrophages are numerous, sinus lining cells are hypertrophic. Erythrophagocytosis is hardly seen by electron microscope. Not all red blood cells are spherocytes. Spherocytes are seen well in electronmicroscopy. We did not observed transition of erythrocytes through sinus walls. In certain circumstances lots of ferritin is seen both intra and extracytoplasmically. Iron accumulation in cords can result in their fibrosis.

Band 4.2 Shiga: 317 CGC-->TGC in compound heterozygotes with 142 GCT-->ACT results in band 4.2 deficiency and microspherocytosis

A novel compound heterozygous mutation of 317 CGC-->TGC with 142 GCT-->ACT in human red cell band 4.2 deficiency is described. A proband and his son suffered from compensated haemolysis with nearly complete deficiency of red cell band 4.2. Their red cell morphology exhibited microspherocytosis resembling classic hereditary spherocytosis (HS). Sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed band 4.2 to be nearly missing (< 1% of normal controls) with the presence of 74 kD and 72 kD isoforms in trace amounts. Other family members (daughters older and younger than the son) exhibited nearly normal amounts of 72kD as a wild form of band 4.2 on SDS-PAGE with the presence of the 74kD isoform in a trace amount. The proband and his son demonstrated two compound heterozygous mutations in trans: i.e. nucleotide (nt) 949 CGC-->TGC (codon 317 Arg-->Cys) in exon 7 and nt 424 GCT--ACT (codon 142 Ala-->Thr) in exon 3 of the band 4.2 gene. The two daughters demonstrated only the mutation of nt 949 CGC-->TGC in exon 7 in heterozygous states, but no 142 mutation. Therefore the proband and his son were compound heterozygotes of these two mutations in trans. It is interesting to note that the 74 kD isoform of band 4.2 protein existed in a trace amount in the two daughters in spite of the absence of the 142 Ala-->Thr mutation. In addition, even in the presence of the 142 mutation in one allele in the proband and his son, their red cell morphology demonstrated classic HS with microspherocytosis, although a homozygous state of the 142 mutation known as the Nippon type of band 4.2 deficiency exhibits ovalostomatocytosis.

MR findings in hereditary spherocytosis

The magnetic resonance findings of intrathoracic extramedullary hematopoiesis associated with bone marrow reconversion, and reticuloendothelial hemosiderosis in a 50-years-old are reported. Radiologic finding of extramedullary hematopoiesis was the first step to the diagnosis of previously unknown hereditary spherocytosis.

Clinical features and splenic pathologic changes in patients with autoimmune hemolytic anemia and congenital hemolytic anemia

We characterized the pathologic changes in 50 spleens from patients with autoimmune hemolytic anemia and in 13 spleens from patients with congenital hemolytic anemia. The major pathologic findings in autoimmune hemolytic anemia were mild to pronounced cord congestion and variable white pulp area, erythrophagocytosis in conjunction with an increased polymorphonuclear neutrophil reaction, and increased deposition of hemosiderin and extramedullary hematopoiesis. In contrast, both the severity and the frequency of polymorphonuclear neutrophil reactions, deposition of hemosiderin, and extramedullary hematopoiesis were less in patients with congenital hemolytic anemia, and prominent cord congestion associated with an empty or collapsed sinus was noted in patients with hereditary spherocytosis. The activity of erythrophagocytosis in the sinus was more distinct in patients with congenital hemolytic anemia, especially those with nonspherocytic congenital hemolytic anemia, than in patients with autoimmune hemolytic anemia. These findings are consistent with the existence of different mechanisms of trapping and destruction of erythrocytes in autoimmune hemolytic anemia and congenital hemolytic anemia.

Splenic sequestration associated with sickle cell trait and hereditary spherocytosis

Coexistence of sickle cell trait and hereditary spherocytosis (HS) is unusual, and only 16 cases have been reported in the literature. These patients have the same clinical and hematological features as individuals having HS alone. We report a serious complication, acute splenic sequestration crisis (ASSC), occurring in two patients with sickle cell trait and HS. One patient experienced four episodes of ASSC during an 11-year span, while the other had two episodes of this complication during a 4-year period. Red blood cell studies and membrane protein analysis confirmed the diagnosis of HS as a consequence of spectrin deficiency. Splenectomy resulted in marked clinical and hematological improvement in both patients. Histological examination of spleens following splenectomy confirmed that significant erythrostasis and sickling had indeed occurred. ASSC can occur in patients with coexistence of sickle cell trait and HS, and this potentially life-threatening complication should be considered in this condition.