Characterization of hereditary red blood cell membranopathies using combined targeted next-generation sequencing and osmotic gradient ektacytometry.

Hereditary red blood cell (RBC) membranopathies are characterized by mutations in genes encoding skeletal proteins that alter the membrane complex structure. Hereditary spherocytosis (HS) is the most common inherited RBC membranopathy leading to hereditary hemolytic anemia with a worldwide distribution and an estimated prevalence, in Europe, of about 1:2000 individuals. The recent availability of targeted next generation sequencing (t-NGS) and its combination with RBC deformability measured with a laser-assisted optical rotational ektacytometer (LoRRca) has demonstrated to be the most powerful contribution to lower the percentage of hereditary hemolytic anemia undiagnosed cases. In order to know the kind and frequency of RBC membrane mutations in our geographical area (Catalonia) and to better understand their pathophysiology, 42 unrelated, non-transfusion-dependent (NTD) patients with hereditary hemolytic anemia have been studied by combining t-NGS and LoRRca. The osmoscan module of LoRRca provides three rheological profiles that reflect the maximal deformability (EImax), osmotic fragility (Omin), and hydration state (Ohyper) of RBCs and contribute to a better understanding of the contribution RBC rheology to the severity of anemia. From the 42 patients studied, 37 were suspected to be a RBC membrane defect due to phenotypic characteristics and abnormal RBC morphology and, from these, in 31 patients (83.8% of cases) the mutation was identified by t-NGS. No definite diagnosis was achieved in 11 patients (26.2% of cases), including 6 out of 37 cases, with suspected membranopathy, and 5 with unclassifiable HHA. In all these undiagnosed patients, the existence of hemoglobinopathy and/or enzymopathy was ruled out by conventional methods.

Congenital Hemolytic Anemia Because of Glucose Phosphate Isomerase Deficiency: Identification of 2 Novel Missense Mutations in the GPI Gene.

Glucose phosphate isomerase (GPI) deficiency is the second most common red blood cell enzymopathy involving the glycolysis pathway. It is an autosomal recessive disorder. Chronic hemolytic anemia is a common manifestation. The most severe one can present as hydrops fetalis. It can also be associated with neurologic dysfunction. We report a girl with severe hemolytic anemia at birth because of GPI deficiency. Enzyme activity assays were inconclusive because of previous blood transfusions. She was found to be compound heterozygous for 2 novel missense mutations, c.490C>A p.(Pro164Thr) and c.817C>T p.(Arg273Cys), in the GPI gene. Other than the chronic hemolytic anemia, she also has mild fine motor, gross motor delay, and developed cerebella ataxia since 5 years old.

A Novel Mutation of Glucose Phosphate Isomerase (GPI) Causing Severe Neonatal Anemia Due to GPI Deficiency.

Glucose-6-phosphate isomerase (GPI) deficiency is very rare, but one of the most common erythroenzymopathies, causing hereditary nonspherocytic hemolytic anemia. This case report describes the clinical features and the molecular etiology of a Dutch patient with GPI deficiency. She is the fifth patient with GPI deficiency identified to date in the Netherlands and was found to be compound heterozygous for the previously reported c.1615G>A p.(Asp539Asn) mutation and a novel c.271A>T p.(Asn91Tyr) variant.

A Rare Cause of Neonatal Hemolytic Anemia: Glutathione Synthetase Deficiency.

BACKGROUND: Isolated hemolysis or hemolytic anemia and 5-oxoprolinuria are 2 distinct medical conditions in the clinical spectrum associated with glutathione synthetase deficiency. CLINICAL OBSERVATION: A 1-day-old female baby presented with anemia and respiratory distress. Her hemoglobin level was 9.5 g/dL and the total serum bilirubin level was 5.6 mg/dL. Metabolic acidosis was detected in her blood gas analysis. Metabolic acidosis recurred despite treatment and further investigation was required. Her 5-oxoproline level was 3815 mmol/mol creatinine in urine organic acid analysis, and a homozygous mutation [p.R125H (c.374G>A)] was found in the glutathione synthetase gene. CONCLUSIONS: GSD has been observed in very few patients and is rarely considered in the differential diagnosis of hemolytic anemia in newborns.

Neonatal nonimmune hemolytic anemia.

PURPOSE OF REVIEW: As in adults and older children, anemia in newborn infants can be the result of erythropoietic failure, hemorrhage, or hemolysis. When hemolysis is the prime consideration, it can be challenging for physicians caring for neonates to choose from the wide variety of available diagnostic tests. This review describes the authors' opinions regarding rational, consistent, and cost-effective means of making an exact diagnosis of a neonatal hemolytic condition. RECENT FINDINGS: Two recent advances in the diagnosis of neonatal nonimmune hemolytic disorders are highlighted in this review: introduction of flow cytometry-based Eosin-5-maleimide (EMA) uptake as a screening test to identify RBC membrane defects and next-generation sequencing (NGS)-based panels to uncover exact mutations causing hemolysis. SUMMARY: The availability of newer tools such as EMA and NGS to diagnose specific hemolytic conditions, which might otherwise remain unknown, enables neonatal practitioners not only to identify the exact cause of hemolysis but also to discover novel mutations that can be implicated in the cause of neonatal hemolytic processes.

ICSH guidelines for the laboratory diagnosis of nonimmune hereditary red cell membrane disorders.

INTRODUCTION: Hereditary spherocytosis (HS), hereditary elliptocytosis (HE), and hereditary stomatocytosis (HSt) are inherited red cell disorders caused by defects in various membrane proteins. The heterogeneous clinical presentation, biochemical and genetic abnormalities in HS and HE have been well documented. The need to raise the awareness of HSt, albeit its much lower prevalence than HS, is due to the undesirable outcome of splenectomy in these patients. METHODS: The scope of this guideline is to identify the characteristic clinical features, the red cell parameters (including red cell morphology) for these red cell disorders associated, respectively, with defective cytoskeleton (HS and HE) and abnormal cation permeability in the lipid bilayer (HSt) of the red cell. The current screening tests for HS are described, and their limitations are highlighted. RESULTS: An appropriate diagnosis can often be made when the screening test result(s) is reviewed together with the patient's clinical/family history, blood count results, reticulocyte count, red cell morphology, and chemistry results. SDS-polyacrylamide gel electrophoresis of erythrocyte membrane proteins, monovalent cation flux measurement, and molecular analysis of membrane protein genes are specialist tests for further investigation. CONCLUSION: Specialist tests provide additional evidence in supporting the diagnosis and that will facilitate the management of the patient. In the case of a patient's clinical phenotype being more severe than the affected members within the immediate family, molecular testing of all family members is useful for confirming the diagnosis and allows an insight into the molecular basis of the abnormality such as a recessive mode of inheritance or a de novo mutation.

Skunk musk causes methemoglobin and Heinz body formation in vitro.

BACKGROUND: A captive Red Panda developed a regenerative anemia with Heinz bodies after being sprayed by a skunk. A definite cause-and-effect relationship between skunk musk and oxidative erythrocyte damage has not been reported, but it was suspected in one reported case of a dog with Heinz body hemolytic anemia. OBJECTIVE: The objective was to determine whether skunk musk induces oxidative HGB damage in vitro. METHODS: Plasma and RBC were harvested from heparinized blood of 3 dogs, 3 cats, and a Red Panda. Skunk musk was solubilized in ethanol and mixed with plasma from each species to make stock solutions of 4% musk and 4% ethanol. Aliquots of RBC were resuspended in autologous stock solutions and solvent controls to yield musk concentrations of 0%, 0.04%, and 0.4% (by volume). Aliquots were incubated at 37°C for 4-72 hours and assessed for oxidative damage by visual inspection, optical absorbance spectroscopy, transmission electron microscopy, and light microscopy after Wright and vital New Methylene Blue staining. RESULTS: Dose-dependent brown color and absorption changes characteristic of methemoglobin were present by 4 hours and increased over 24 hours (Red Panda) and 72 hours (dog and cat). Similarly, there were time-dependent (all species) and dose-dependent (dog and cat) increases in the number of Heinz bodies, which were present by 4 hours and numerous by 24 hours. CONCLUSIONS: In vitro, skunk musk causes Heinz body and methemoglobin formation in canine, feline, and Red Panda RBC, supporting the clinical association between Heinz body hemolytic anemia and skunk spray exposure.

Six children with pyruvate kinase deficiency from one small town: molecular characterization of the PK-LR gene.

We identified the pyruvate kinase liver/red cell enzyme gene mutation of 8 children previously diagnosed with pyruvate kinase deficiency who were living in a remote town in the western United States. Six were found to be homozygous for the mutation 1529G-A (510 Arg-Gln). Two previously thought to have pyruvate kinase deficiency did not, because they were heterozygous.

Hemoglobin J--as a cause of congenital hemolytic anemia.

Hemoglobin-J is a rare hemoglobin variant known to be clinically silent most of the times, only to be detected accidentally. Herein, the authors report a case of Hemoglobin-J manifesting as unstable hemoglobin detected during evaluation of hemolytic anemia in an 8 month-old-infant. Cation Exchange-High Performance Liquid Chromatography(CE-HPLC) was used to identify this variant after Hb electrophoresis was reported to be normal.

Red cell pyruvate kinase deficiency in Southern Sardinia.

Pyruvate kinase (PK) deficiency is the most frequent red cell enzymatic defect responsible for hereditary non-spherocytic hemolytic anemia. The clinical picture is quite variable and the reasons of this variability have been only partially clarified. We report the clinical description and the extended molecular analysis in 3 PK deficient patients with clinical phenotype of variable severity. We studied the clinical and hematological aspects of 3 patients and analyzed the following genes: pyruvate kinase-R, glucose-6-phosphate-dehydrogenase, α-globin, uridindiphosphoglucuronil transferase and HFE. One patient (A) with a severe clinical picture resulted homozygote for exon 8 nt994A substitution, the other 2 (brothers) were compound heterozygotes for exon 8 nt994A and exon 11 nt1456T mutation. One of the two brothers with a more severe phenotype coinherited also had G6PD deficiency, while both had microcytosis due to the homozygosity for the non-deletional form of α-thalassemia ATG→ACG substitution at the initiation codon of the alpha2 globin gene. Our results suggest that extended molecular analysis is useful for studying how several interacting gene mutations contribute to the clinical variability of pyruvate kinase deficiency.