Thalassemia Intermedia Phenotype Research Articles

Unravelling the Complexity of the +33 C>G [HBB:c.-18C>G] Variant in Beta Thalassemia.

The +33 C>G variant [NM_000518.5(HBB):c.-18C>G] in the 5' untranslated region (UTR) of the β-globin gene is described in the literature as both mild and silent, while it causes a phenotype of thalassemia intermedia in the presence of a severe β-thalassemia allele. Despite its potential clinical significance, the determination of its pathogenicity according to established standards requires a greater number of published cases and co-segregation evidence than what is currently available. The present study provides an extensive phenotypic characterization of +33 C>G using 26 heterozygous and 11 compound heterozygous novel cases detected in Cyprus and employs computational predictors (CADD, RegulomeDB) to better understand its impact on clinical severity. Genotype identification of globin gene variants, including α- and δ-thalassemia determinants, and rs7482144 (XmnI) was carried out using Sanger sequencing, gap-PCR, and restriction enzyme digestion methods. The heterozygous state of +33 C>G had a silent phenotype without apparent microcytosis or hypochromia, while compound heterozygosity with a β+ or β0 allele had a spectrum of clinical phenotypes. Awareness of the +33 C>G is required across Mediterranean populations where β-thalassemia is frequent, particularly in Cyprus, with significant relevance in population screening and fetal diagnostic applications.

Compound heterozygous delta beta thalassemia with IVS 1-5 (G>C) mutation presenting as thalassemia major phenotype

Delta beta thalassemia is an unusual variant of thalassemia with elevated level of fetal hemoglobin (HbF). Unlike beta thalassemia, delta beta thalassemia heterozygotes have milder phenotype and homozygotes present as thalassemia intermedia phenotype. We report a 11-month-old male child who presented with severe anemia, and hepatosplenomegaly, thalassemia major phenotype. On evaluation was diagnosed as compound heterozygous for δβ0/β thalassemia with IVS 1-5 (G>C) mutation. This case highlights the importance of genotyping of patients with δβ thalassemia and co-inheritance of δβ thalassemia deletion with point mutation for β-thalassemia results in severe clinical phenotype as thalassemia major.

Interactions of unstable hemoglobin Rush with thalassemia and hemoglobin E result in thalassemia intermedia

ABSTRACTBackground: The clinical consequences and significance of many unstable hemoglobins interacting with other hemoglobinopathies remain unrecognized. Here we first explore molecular and hematological characterizations of previously undescribed compound heterozygosity states for unstable hemoglobin Rush (Hb Rush, Beta 101 Glu > Gln, HBB:c.304G > C) with Hb E and different forms of thalassemia.Methods: Hematological assays, globin gene mutation assays and β-globin gene cluster haplotype were conducted in 11 patients from 8 unrelated Chinese ethnic families with unexplained hemoglobin separation fraction in hemoglobin gel electrophoresis.Results: Hb Rush in various combinations with Hb E, β0-thalassemias and α+-thalassemia were identified. Hb Rush simple heterozygote was generally associated with mild hemolytic anemia, and the compound heterozygotes of Hb Rush and the other β-globin variants led to thalassemia intermedia phenotypes with moderate anemia. Hemoglobin electrophoreses showed that the co-presence of Hb Rush with either Hb E or β0-thalassemias increased proportion of Hb Rush due to relative decrease of other globin chain synthesis. Beta-globin gene cluster haplotype analysis suggested a common origin of the Hb Rush variant in the Chinese families of different ethnic ancestry.Conclusions: Unstable Hb Rush interacting with β-thalassemia result in thalassemia intermedia phenotypes, which demonstrated the clinical significance of Hb Rush and new insights into complex mechanism of clinical heterogeneity of thalassemia.

The phenotypic and molecular diversity of hemoglobinopathies in India: A review of 15 years at a referral center

The hemoglobinopathies pose a significant health burden in India. Apart from the β thalassemias and sickle cell disorders, α thalassemias and structural hemoglobin variants are also common. Here we have reviewed the phenotypic and molecular diversity of hemoglobinopathies encountered at a referral center in western India over a period of 15years. Screening for hemoglobinopathies was done using HPLC and cellulose acetate electrophoresis. Molecular characterization was done using Covalent Reverse Dot Blot Hybridization (CRDB), Amplification Refractory Mutation System (ARMS), GAP PCR and direct DNA sequencing. The study includes 31075 individuals who were referred for diagnosis of hemoglobinopathies and prenatal diagnosis. Of these 14423 individuals showed various hemoglobin abnormalities. Beta genotyping in 5615 individuals showed the presence of 49 β thalassemia mutations. 143 β thalassemia heterozygotes had normal or borderline HbA2 levels. We identified three δ gene mutations (HbA2 Pellendri, HbA2 St.George, HbA2 Saurashtra) in β thalassemia heterozygotes leading to normal HbA2 levels. The commonest defects among the raised Hb F determinants were Gγ(Αγδβ)0 Indian inversion and the HPFH-3 Indian deletion. A total of 312 individuals showed the presence of α thalassemia, of which 12.0% had a single α gene deletion (-α/αα). HbH disease was identified in 29 cases with 10 different genotypes. Alpha globin gene triplication was seen in 2.1% of β thalassemia heterozygotes with a thalassemia intermedia phenotype. Seven unusual α chain variants and eight uncommon β chain variants were identified. The repertoire of molecular defects seen in the different globin genes will be valuable for management and control of these disorders both in India as well as in other countries where there is a huge influx of migrant populations from India.

Alpha Hemoglobinophaties in Rosario, Argentina

Hemoglobinopathies are the most common recessive diseases worldwide. While the molecular basis of β-thalassemia in Rosario has been addressed, that of α-thalassemia and α structural alterations, has not. In this study 105 individuals from different families referred to our center were investigated for alpha hemoglobinopathies because of low MCV (<85 fL), low MCH (<27 dg), normal HbA2 (≤3.5%) and transferrin saturation of >15%. Six of them with a clinical phenotype of thalassemia intermedia were diagnosed as Hb H disease (five cases) and Hb H like (one case). It also included one patient with sickle cell trait, confirmed by hematological and molecular studies. We were able to identify alpha globin genes mutations in 92 individuals (87.6%): 88 patients with alpha thalassemia, 3 patients with structural alterations and one with both. In total, 13 individuals (12.4%) had no identified α-globin mutation. This study is the first to deal with the molecular basis of α-hemoglobinophaties in Rosario.

Clinical and haematological features of Non-Deletional alpha thalassaemia mutations in singapore

Aims Non-deletional mutations of the α-globin gene are rare causes of alpha thalassaemia. Our study aims to characterise the frequency, haematological and clinical features of non-deletional forms of alpha thalassemia in patients who presented to the Singapore National Thalassaemia Registry (NTR) from 1997 to 2012. Methods A list of patients with non-deletional α-globin mutations were generated from laboratory records at the NTR. The relevant patient casenotes were retrieved for clinical details. Results There were 83 patients identified. The three most common α-globin chain mutations were Hb Constant-Spring (CS) (47%), Hb Quong Sze (QS) (14.5%) and Hb Adana (CD59) (12%). There were distinct ethnic differences noted in the distribution of the mutations, as the majority of patients with HbCS (46%) and all patients with HbQS were of Chinese ethnicity whereas most patients with Hb Adana (93%) were of Malay ethnicity. The majority of patients were asymptomatic carriers. Most patients with a thalassaemia intermedia phenotype had HbH disease, co-inheriting deletional α-globin mutations with non-deletional mutations, most commonly --SEA/αCS α in 80% of cases. Coinheritance of Hb Adana / Hb CS (αCS α / α a) in particular was associated with considerable clinical heterogeneity, ranging from asymptomatic carriers to transfusion dependence. Discussion Non-deletional α-globin chain mutations are associated with diverse clinical and haematological features, depending on the specific mutation and interaction with other a and β-globin chain mutations.

Darbepoetin alfa for the treatment of anaemia in alpha‐ or beta‐ thalassaemia intermedia syndromes

Darbepoetin alfa for the treatment of anaemia in alpha‐ or beta‐ thalassaemia intermedia syndromes

Severe Thalassemia Intermedia Resulting From Coinheritance of IVSI-110 G>A Beta Gene Mutation and Duplication of Alpha-Globin Gene Cluster in Homozygosis.

Abstract 2011Poster Board I-1033 IntroductionThe clinical severity of thalassemia intermedia depends on the degree of a/non-a-chains iimbalance. Among the molecular mechanisms responsible for thalassemia intermedia is the coinheritance of excessive a-globin gene production with a defective beta-globin gene. Materials and Methods:we describe an Italian family where thalassemia intermedia apparently segregates as a dominant form but it tourned out to be due to the coinheritance of a beta-globin mutation and a duplication of the alpha-globin gene cluster. The father (aged 51yrs) showed a well tolerated severe chronic hemolytic anemia (Hb 7.5-8.5 g/dL) not transfusion dependent, jaundice, splenomegaly and leg ulcers:The mother (aged 46yrs) has a completely normal hematological and hemoglobin pattern. Two sons (19 and 14 yrs) showed more severe clinical manifestations than the father. They underwent splenectomy at 12 and 13 years respectively without any benefit and afterwards they become transfusion dependent. Results:The hemoglobin analysis revealed that the father and the sons were heterozygotes for the beta mutation IVSI-110 G>A. MLPA analysis of the alpha-globin gene cluster disclosed a full duplication of the alpha-globin locus, spanning a 175 kb from the telomere to the 3'HVR downstream of the alpha-globin gene and including the upstream regulatory element HS-40. This rearrangement increases the number of the active alpha-globin genes in cis from 2 to 4.Surprisengly it was found in heterozygosis in both parents and in homozygosis in both sons. The hematological and molecular data of the family are reported in the table.In the father the 6 alpha-globin genes led to increased synthesis of alpha-chains; the coinheritance with a beta-thalassemia mutation causes a moderate/severe thalassemia intermedia phenotype. The presence of 8 alpha-globin genes in the sons raises further the degree of globin-chains imbalance and exacerbates the clinical phenotype. It is important to note that splenectomy worsened the clinical course.in the 2 homozygotes for the alpha duplication. Conclusions:Based also on previous experience we suggest that splenectomy in patients with a real excess of alphaa chain production is unconvenient since a large amount of circulating red cells with precipitated alpha chains may be responsible for increased hemolysis as well as increased risk of thrombosis This family moreover raises concerns regarding genetic counselling, suggesting that whenever one of the partner is affected by TI it is advisable a complete molecular screening of the couple in order to exclude any possible alpha gene defects interactionAge/genderHb g/dLRBC X1012/LMCV fLMCH pgHbA2 %HbF %Retics %SpleenTransfusionChelationa genesβ genesMother46/F12.84.8781.726.32.50.91.29normalnonoaa,aa/aaβN/βNFather51/M8.54.4764.019.05.03.72.3520 cmnonoaa,aa/aaβT/βNSon19/M6.03.8060.016.54.37.57.57splenectomyyesyesaa,aa/aa,aaβT/βNSon14/F5.93.6959.916.04.07.710.61splenectomyyesyesaa,aa/aa,aaβT/βN Disclosures:No relevant conflicts of interest to declare.

Association of globin gene quadruplication and heterozygous thalassemia in patients with thalassemia intermedia

Ten patients with thalassemia intermedia with variable severity and apparent simple heterozygosis for beta0 39 C>T nonsense mutation were submitted to clinical, hematologic and molecular studies. The presence of an unknown molecular defect (silent beta-thalassemia) unlinked to the beta cluster interacting with the heterozygous beta thalassemia, was previously postulated in these families. Analysis of the alpha globin gene cluster with PCR-based methods (MLPA, GAP-PCR, digestion with restriction enzymes) detected complex rearrangements in the alpha cluster. A duplication of the alpha globin gene locus, including the upstream regulatory region, was present in all the patients, associated in some of them with deletion or non-deletion alpha thalassemia. The variability of the clinical phenotype correlates with the degree of the globin chain imbalance. The presence of alpha globin cluster duplication should be considered in patients heterozygote for beta-thalassemia with thalassemia intermedia phenotype and in the carriers of suspected silent beta thalassemia.

Molecular Mechanisms Underlying Thalassemia Intermedia in Iran

To improve the differentiation of thalassemia intermedia from other hemoglobinopathies in Iran, four known genetic mechanisms-XmnI (G)gamma polymorphism, inheritance of mild and silent beta-thalassemia alleles, delta beta deletion, and coinheritance of alpha- and beta-thalassemia-were investigated in 52 Iranian individuals suspected to have thalassemia intermedia based on clinical and hematological characteristics. Beta-globin mutations were studied using a reverse-hybridization assay and sequencing of the total beta-globin gene. The XmnI (G)gamma polymorphism, the Sicilian delta beta deletion, and four alpha-globin mutations (-a(3.7), -a(4.2), -(MED), aaa(anti-3.7)) were studied using PCR-based techniques. The inheritance of the XmnI (G)gamma polymorphism with severe beta-thalassemia alleles in the homozygous or compound heterozygous state was the predominant mechanism observed in 27 individuals (55.3%). In five cases, this status overlapped with the -a(3.7)/aa genotype. The second most frequent cause for thalassemia intermedia (14.8%) was the inheritance of mild beta-thalassemia alleles, including IVS-I-6 (T > C), -88 (C > A), and + 113 (A > G). In three subjects (4.3%) the Sicilian delta beta deletion was identified. HbS in association with beta-zero-thalassemia was found in three patients with thalassemia intermedia phenotype. In 11 cases (21.3%) no causative genetic alteration could be identified. Our results reflect the diversity underlying thalassemia intermedia, and the limitations of the applied clinical, hematological, and molecular approaches for correct diagnosis. Some of the unresolved cases will offer an opportunity to discover additional molecular mechanisms leading to thalassemia intermedia.

In vivo selection of genetically modified erythroblastic progenitors leads to long-term correction of β-thalassemia

Gene therapy for beta-thalassemia requires stable transfer of a beta-globin gene into hematopoietic stem cells (HSCs) and high and regulated hemoglobin expression in the erythroblastic progeny. We developed an erythroid-specific lentiviral vector driving the expression of the human beta-globin gene from a minimal promoter/enhancer element containing two hypersensitive sites from the beta-globin locus control region. Transplantation of transduced HSCs into thalassemic mice leads to stable and long-term correction of anemia with all red blood cells expressing the transgene. A frequency of 30-50% of transduced HSCs, harboring an average vector copy number per cell of 1, was sufficient to fully correct the thalassemic phenotype. In the mouse model of Cooley's anemia transplantation of transduced cells rescues lethality, leading to either a normal or a thalassemia intermedia phenotype. We show that genetically corrected erythroblasts undergo in vivo selection with preferential survival of progenitors harboring proviral integrations in genome sites more favorable to high levels of vector-derived expression. These data provide a rationale for a gene therapy approach to beta-thalassemia based on partially myeloablative transplantation protocols.

Segmental duplications involving the α-globin gene cluster are causing β-thalassemia intermedia phenotypes in β-thalassemia heterozygous patients

We describe two cases of simple heterozygosity for the common β°-thalassemia mutation β39 (C → T), both presenting with a thalassemia intermedia phenotype. In both cases synergic effect deriving from membrane defects or red cell enzyme deficiencies were excluded. In one case a triplication of the α-globin genes was found which did not justify the severity of the transfusion-dependent phenotype. Multiplex ligation-dependent probe amplification (MLPA) analysis of the α-globin gene cluster revealed two new rearrangements, consisting of a full duplication of the α-globin genes locus including the upstream regulatory element. In one case the duplication was in the presence of the common anti-α 3.7 triplication in trans, resulting in a total of 7 active α-globin genes. In the other case the duplicated allele and the normal allele in trans resulted into a total of 6 active α-globin genes. We report the clinical and hematological data and the molecular analysis and discuss the occurrence of α-globin genes duplication defects in cases of β-thalassemia heterozygotes with thalassemia intermedia phenotypes.

First Observation of Hb Taybe [Codons 38/39 (−Acc) Thr→0 (α1)] In Greece: Clinical and Hematological Findings in Patients With Co-Inherited α+-Thalassemia Mutations

This report describes four unrelated Greek patients (one child and three adults) who all had an atypical thalassemia intermedia phenotype, characterized by chronic moderate anemia with mild hemolysis in some cases, and the absence of abnormal hemoglobin (Hb) fractions. DNA analysis identified the inheritance of common α+-thalassemia (α+-thal) mutations in trans to an in-frame 3 bp deletion at codons 38/39 (−ACC) on the α1-globin gene, previously described as Hb Taybe. Hematological findings in the parents of three of the Hb Taybe carrier cases, together with a fourth unrelated carrier, are also presented. These cases represent the first observation of Hb Taybe in the Greek population, as to date, it has only been observed in Israeli-Arab families. With the exception of one patient and his mother who both originate from Corfu, all our cases come from the Greek island of Crete.

Molecular Basis of Thalassemia Intermedia in Iran

Thalassemia intermedia shows considerable heterogenity in phenotype and molecular basis. The aim of this study was to evaluate the prevalence and effect of different β-globin mutations, α-globin defects and Gγ XmnI polymorphisms in Iranian patients. Forty-five Iranian patients with clinical criteria of thalassemia intermedia were studied. The molecular background of the diseases was investigated. The mean age of onset varied from 1.5 to 30 years. Only 22.2% of cases received occasional blood transfusions. The hemoglobin (Hb) level in more than half of the cases was stable (10–12 g/dL) with no need for blood transfusions. In most cases (88.9%) the Hb F level was more than 50%. Sixty-eight point nine percent of patients were homozygous for β0-thalassemia (β-thal) mutations. The positive XmnI polymorphism with the capability of enhancing Hb F production was seen in 60% of the studied chromosomes. Co-inheritance of α-globin gene defects was seen in 22.2% of cases. Only 8.9% of patients had β+ or β++ mutations.We concluded that the main molecular basis of the thalassemia intermedia phenotype in Iranian cases is co-inheritance of a positive XmnI polymorphism with β-globin mutations, which can enhance the capability of Hb F production. Co-inheritance of α-globin defects and mild β-globin mutations are second and third causes of thalassemia intermedia phenotypes respectively. These factors must be considered in genetic counseling, prediction of disease prognosis and treatment and prenatal diagnosis.

Further Identification of The Hyperunstable α-Globin Chain Variant Hb Heraklion [codons 36/37 (–CCC); Pro→0 (α1)] in Greek Cases With Co-Inherited α+-Thalassemia Mutations

We report four Greek cases (from three unrelated families), who all had a similar atypical thalassemia intermedia phenotype, characterized by chronic moderate anemia, mild hemolysis and splenomegaly in the absence of abnormal hemoglobin (Hb) fractions. In all four cases (two unrelated children and two siblings), DNA analysis identified common α+-thalassemia (α+-thal) mutations in trans to the in frame 3 bp deletion (−CCC) on the α1-globin gene between codons 36 and 37, which has previously been reported as Hb Heraklion in a single Greek case. Clinical, hematological and biochemical findings in all cases, including a follow-up evaluation of the original case, are described. All the cases originated from the Greek island of Crete.

Haematological and clinical features of β‐thalassaemia associated with Hb Dhofar

Hb Dhofar is a variant haemoglobin (beta(29 (GGC-GGT) gly-gly), beta(58 (CCT-CGT) pro-arg)) associated with a thalassaemic phenotype and unique to the Sultanate of Oman. We report clinical and haematological data on 54 subjects with Hb Dhofar (37 heterozygotes, 14 homozygotes and three compound heterozygotes with a different beta-thalassaemia mutation). In heterozygotes, the level of Hb Dhofar ranged from 8.8% to 21.5%. All heterozygotes had Hb A2 > 3.5%, consistent with beta-thalassaemia trait. Hb Dhofar in homozygotes and compound heterozygotes ranged from 26% to 59.7%, with a peripheral film consistent with homozygous beta-thalassaemia. Age at presentation in homozygotes ranged between 6 months and 8 yr, with a majority presenting before 5 yr of age. All had splenomegaly and six (43%) had undergone splenectomy. All had some degree of frontal bossing and in particular, two patients with infrequent transfusions had marked thalassaemic facies and stunting of growth. Hb Dhofar can be mistaken for Hb D as the electrophoretic mobility is similar, but differs from it by a variable and reduced quantity of variant Hb in both heterozygotes and homozygotes. Clinical and haematological data suggest that this mutation behaves like a moderately severe beta(+) thalassaemia allele resulting in a thalassaemia intermedia phenotype.

Improved Human β-globin Expression from Self-inactivating Lentiviral Vectors Carrying the Chicken Hypersensitive Site-4 (cHS4) Insulator Element

Effective gene therapy for beta-thalassemia major (beta-TM) requires consistent, high expression of human beta-globin (hbeta-globin) in red blood cells (RBCs). Several groups have now shown that lentiviral (LV) vectors stably transmit the hbeta/hgamma-globin genes and large elements of the locus control region, resulting in correction of the murine thalassemia intermedia (TI) phenotype and survival of mice with the TM phenotype. However, current LVs show variable hbeta/hgamma-globin expression and require a high number of vector copies/cell for a therapeutic effect. To address this, we designed LVs flanked by the chicken hypersensitive site-4 (cHS4) chromatin insulator element and compared them with their "un-insulated" counterparts. We observed a consistent twofold-higher hbeta expression from insulated vectors in single-copy mouse erythroleukemia cell clones, an increase that resulted from reduced position effect variegation (PEV) and increased probability of expression from individual integrants. This effect was confirmed in vivo: an approximately twofold increase in hbeta expression was seen in the RBC progeny of murine hematopoietic stem cells, with significantly higher numbers of hbeta-expressing cells in individual secondary spleen colony-forming units. In summary, cHS4-insulated hbeta-globin LVs showed distinct chromatin barrier activity, resulting in higher, consistent hbeta expression. These studies have important implications for vector design for clinical trials for gene therapy for hemoglobinopathies.

Thalassemia Intermedia Due to a Novel Mutation in the Second Intervening Sequence of the β-Globin Gene

We describe a new β-thalassemia (thal) mutation in the β-globin gene of an 8-year-old Moroccan boy. This homozygous mutation produces a phenotype of thalassemia intermedia and is associated with the Mediterranean haplotype IX. We discuss the pathophysiological consequences of this mutation which is located near the 3 ′ end of the second intervening sequence (IVS-II) of the β-globin gene.

AHSP Promoter Homopolymer in Beta-Thalassemia Syndromes.

Alpha hemoglobin stabilizing protein (AHSP) is an erythroid protein that binds specifically to the alpha globin chains to form a stable complex, preventing their precipitation before the assembly of the hemoglobin tetramere. Studies have shown thatAHSP is required for normal erythropoiesis,knock-out mice has a phenotype similar to beta thalassemia,loss of AHSP worsens the severity of the disease in thalassemic mice.Therefore, altered AHSP expression or function could account for some of the variability in beta-thalassemia phenotype. At position -160bp upstream of exon 1 of the AHSP gene, two main homopolymers (T18 and T15) have been reported that may influence the AHSP expression and hence the hematological phenotype. In particular the frequence of the shorter T15 homopolymer, which is associated with a lower AHSP expression, was much higher than expected (on the basis of the allele frequency in the healthy population) in a group of 9 patients with thalassemia intermedia, due the compound heterozygosity for beta-thalassemia and the triple alpha globin gene (Mei et al, 2006). We have studied the frequency of T15 and T18 homolpolymers in a group of 20 normal subjects and in patients with different thalassemia syndromes, i.e. beta zero 39 homozygotes with thalassemia major (14 patients) and intermedia (19), compound heterozygotes for beta-thalassemia and triple alpha globin gene (13) and simple carriers for beta thalassemia with thalassemia intermedia phenotype (5). We found the following genotype distribution reported in figure1. There is no difference in the frequency of the genotypes among the groups, except in the severe beta-thalassemia carriers, where the short T15 homopolymer is more common. These findings are consistent with the reduced AHSP expression previously reported in the reticulocytes and in the erythroid cultures of these unusually severe beta thalassemia carriers. (Galanello et al, abs 1881. ASH 2003). Therefore, only in the peculiar group of beta-thalassemia carriers with the clinical features of thalassemia intermedia, the AHSP genotype appears to be a relevant contributory factor in the hematological phenotype. [Display omitted]

Hemoglobin H Hydrops Fetalis Associated with Homozygous Hemoglobin Constant Spring. Case Report.

While Barts hydrops is predicted when all 4 α globin genes are absent or non functional, hydrops has rarely been described with a hemoglobin H (Hb H) genotype. Hb H disease has a varied hematologic phenotype ranging from asymptomatic to transfusion dependant. The severest clinical expression is non immune hydrops and may result in fetal demise. The commonest form of Hb H disease is deletional-type. This occurs when there is deletion of α2 and α1 genes in cis and deletion of either α2 or α1 in trans. The less frequent type, but clinically more severe, is non-deletional. This is usually due to a mutation in either α2 or α1 in cis and a deletion of both α2 and α1 in trans. There are rare reports of non-deletional Hb H due to homozygous α2 mutations without any α1 deletions or mutations. Heretofore, there have been no reports of hydrops with homozygous hemoglobin Constant Spring (Hb CS). A 31-year-old Laotian woman presented at 22 weeks with polyhydramnios. Besides this, the pregnancy was uneventful for the mother. On ultrasound the fetus had a pericardial effusion and signs of congestive heart failure. The hematological and genotypic parameters of the parents and fetus are outlined in table 1. Intrauterine transfusions were performed at 22 and 29 weeks. A male infant was born vaginally at 36 weeks gestation weighing 2.3 kg. The hemoglobin was 15.9 g/dL and bilirubin was 8.4mg/dL. There was no evidence of maternofetal alloimmunization. G6PD screen was negative. By 4 weeks post-partum, the bilirubin had decreased to 0.9 mg/dL but the hemoglobin had progressively fallen to 6.9 g/dL, requiring transfusion. He had two additional transfusions at 6 and 8 weeks of life but has subsequently maintained a hemoglobin above 10 g/dL and has steadily gained weight. As in this patient, the genotypes of the other reported cases of Hb H hydrops are usually associated with a thalassemia intermedia phenotype. Thus the α globin genotypes alone do not explain why hydrops occurs. This suggests that there may be unknown genetic and/or acquired modifiers contributing to the severity of Hb H disease that results in hydrops as in this fetus with homozygous Hb CS.[Table 1]MotherFatherFetus at 22 weeksHemoglobin g/dL10.012.55.2MCV fL86.381.8143.8MCH pg26.525.6.846.4RDW %16.713.621.4Reticulocyte %9.9ND19.0NRBC/100WBC104756Hemoglobin Fractions by HPLCHb A73.3%97.8%3.4%Hb F0.8%0.0%77.7%Hb A20.9%2.1%0.0%Barts0.0%0.0%17.7%Hb Constant Spring2.8%0.1%1.2%HbE 22.2%0.0%0.0%αGlobin Gene Dosage Assay by Linear PCR444αGlobin Gene Deletions by PCR - 3.7, - 4.2, _SEA, - 20.5, _MED,_FIL,_THAINone detectedNone detectedNone detectedα2 Globin Gene Sequencingα-2CS/α-2CSα-2CS/WTα-2CS/α-2CSα1 Globin Gene SequencingWT/WTWT/WTWT/WTβGlobin Gene SequencingHeterozygous Hb EWT/WTWT/WT E