Gata1-Related X-Linked Cytopenia

Clinical characteristics.

GATA1-related cytopenia is characterized by thrombocytopenia and/or anemia ranging from mild to severe. One or more of the following may also be present: platelet dysfunction, mild β-thalassemia, neutropenia, and congenital erythropoietic porphyria (CEP) in males. Thrombocytopenia typically presents in infancy as a bleeding disorder with easy bruising and mucosal bleeding (e.g., epistaxis). Anemia ranges from minimal (mild dyserythropoiesis) to severe (hydrops fetalis requiring in utero transfusion). At the extreme end of the clinical spectrum, severe hemorrhage and/or erythrocyte transfusion dependence are life long; at the milder end, anemia and the risk for bleeding may decrease spontaneously with age. Heterozygous females may have mild to moderate symptoms such as menorrhagia.

Diagnosis/testing.

Diagnostic laboratory findings usually include macrothrombocytopenia (low number of platelets that are larger than normal) and/or anemia with red cell indices that may be micro-, normo- or macrocytic. Defects in platelet aggregation in response to agonists may be seen. In some cases electron microscopy reveals reduced numbers of platelet alpha granules and dysplastic features in platelets and megakaryocytes.

Management.

Treatment of manifestations: Platelet transfusions for moderate to severe epistaxis, gingival bleeding, or gastrointestinal bleeding; no specific treatment for mild symptoms (easy bruisability); erythrocyte transfusions when anemia is symptomatic (fatigue, tachycardia).

Prevention of primary manifestations: For severe cases, bone marrow transplantation (BMT) can be curative.

Surveillance: Monitoring complete blood counts (with frequency depending on disease severity) to inform supportive care; monitoring those undergoing repeated erythrocyte transfusions for iron overload.

Agents/circumstances to avoid: Those with thrombocytopenia should avoid antiplatelet agents including aspirin and nonsteroidal anti-inflammatory agents (e.g., ibuprofen). Those with thrombocytopenia and/or platelet aggregation defects should avoid contact sports or activities with a high risk of trauma.

Evaluation of relatives at risk: If a GATA1 pathogenic variant has been identified in the family, complete blood counts and molecular genetic testing of at-risk relatives can be offered. At-risk relatives who choose not to have molecular genetic testing should have complete blood counts to evaluate for thrombocytopenia, anemia, or neutropenia.

Genetic counseling.

GATA1-related cytopenia is inherited in an X-linked manner. If the mother of an affected male has a GATA1 pathogenic variant, the chance of transmitting it in each pregnancy is 50%. Affected males pass the pathogenic variant to all of their daughters and none of their sons. Testing for at-risk family members and prenatal testing for a pregnancy at increased risk are possible once the pathogenic variant has been identified in the family.

Suggestive Findings

GATA1-related cytopenia should be suspected in an individual with the following:

• Thrombocytopenia and/or anemia ranging from mild to severe (including fetal hydrops)
• One or more of the following:
  • Platelet dysfunction
  • Mild β-thalassemia
  • Neutropenia
  • Congenital erythropoietic porphyria (CEP)
• Family history consistent with X-linked inheritance
• No evidence of Wiskott-Aldrich syndrome (WAS), an X-linked disorder of microthrombocytopenia that can present with or without immunodeficiency

Note: 1) Initial testing should include complete blood count, examination of the blood smear, and bone marrow aspirate and biopsy to confirm that cytopenia results from ineffective hematopoiesis rather than peripheral destruction or sequestration. 2) Hematologic findings in GATA1-related cytopenia are variable and usually nonspecific (i.e., seen in numerous conditions and thus by themselves not indicative of a specific diagnosis). 3) Affected individuals are typically male; females will usually present with milder findings.

Establishing the Diagnosis

Male proband. The diagnosis of GATA1-related cytopenia is established in a male proband with cytopenia resulting from ineffective hematopoiesis by identification of a hemizygous pathogenic variant in GATA1 by molecular genetic testing (see Table 1).

Female proband. The diagnosis of GATA1-related cytopenia may be established in a female proband with hematopoietic cytopenias by identification of a pathogenic variant in GATA1 by molecular genetic testing (Table 1). A pattern of skewed X-inactivation would support the diagnosis. Note: This disorder is not usually first diagnosed in a family via a female proband.

Molecular testing approaches can include single-gene testing, use of a multigene panel, and more comprehensive genomic testing:

• Single-gene testing. Sequence analysis of GATA1 is performed. Although no exon or whole-gene deletions or duplications have been reported as a cause of GATA1-related cytopenias, some laboratories offer gene-targeted deletion/duplication analysis if a pathogenic variant is not found.
• A multigene panel that includes GATA1 and other genes of interest (see Differential Diagnosis) may be considered. Note: (1) The genes included in the panel and the diagnostic sensitivity of the testing used for each gene vary by laboratory and are likely to change over time. (2) Some multigene panels may include genes not associated with the condition discussed in this GeneReview; thus, clinicians need to determine which multigene panel is most likely to identify the genetic cause of the condition at the most reasonable cost while limiting identification of variants of uncertain significance and pathogenic variants in genes that do not explain the underlying phenotype. (3) In some laboratories, panel options may include a custom laboratory-designed panel and/or custom phenotype-focused exome analysis that includes genes specified by the clinician. (4) Methods used in a panel may include sequence analysis, deletion/duplication analysis, and/or other non-sequencing-based tests.
  For an introduction to multigene panels click here. More detailed information for clinicians ordering genetic tests can be found here.
• More comprehensive genomic testing (when available) including exome sequencing and genome sequencing may be considered. Such testing may provide or suggest a diagnosis not previously considered (e.g., mutation of a different gene or genes that results in a similar clinical presentation). For an introduction to comprehensive genomic testing click here. More detailed information for clinicians ordering genomic testing can be found here.

Clinical Description

Individuals with GATA1-related cytopenia have thrombocytopenia and/or anemia.

Males

• Males typically present in infancy with a bleeding disorder:
  • Affected individuals have easy bruising and mucosal bleeding (e.g., epistaxis).
  • Physical examination may reveal petechiae, ecchymoses, or splenomegaly.
  • Excessive hemorrhage and/or bruising can occur either spontaneously or after trauma or surgery.
• Anemia, the other major clinical problem in males with this disorder, ranges from minimal with only mild dyserythropoiesis [Freson et al 2001] to severe hydrops fetalis requiring in utero transfusions [Nichols et al 2000].
  • Anemia can be so severe that affected males are red blood cell transfusion dependent from birth [Freson et al 2002].
  • In one family, moderately severe anemia was associated with congenital erythropoietic porphyria (CEP) with no pathogenic variants detected in UROS; an Arg216Trp pathogenic variant was identified in GATA1 [Phillips et al 2007]. The affected individual also had bullous skin lesions associated with porphyria. In two additional probands with CEP, anemia and thrombocytopenia, a pathogenic variant in UROS or SEC23B was detected in addition to an Arg216Trp variant in GATA1 [Di Pierro et al 2015].
  • Variable mild to moderate neutropenia with macrocytic anemia and normal platelet counts has been reported in association with a germline pathogenic variant resulting in a truncated protein (GATA-1s; discussed in Molecular Genetics, Pathogenic variants) [Hollanda et al 2006, Sankaran et al 2012, Zucker et al 2016]; family members with severe neutropenia were predisposed to infection [Hollanda et al 2006].
• Splenomegaly is commonly present in one form of GATA1-related disease (see Genotype-Phenotype Correlations). Typically, no other physical anomalies are present.

Laboratory findings in males

• Complete blood count showing the following:
  • Platelet counts are usually low (10-100 x 10³/µL), but vary considerably with specific pathogenic variants. Normal counts have also been reported (150-400 x 10³/µL), including individuals with a germline pathogenic variant resulting in a truncated protein (GATA-1s; see Molecular Genetics, Pathogenic variants) causing congenital anemia [Hollanda et al 2006, Sankaran et al 2012]. The platelets are typically larger than normal (macrothrombocytopenia).
  • Anemia (hematocrit 16%-35%; normal: 35%-45%) may be present; the severity varies with the specific pathogenic variant. Red cell indices are normochromic but may be mildly microcytic (75-79 fL) or macrocytic (101-103 fL) (normal: 80-99 fL).
  • Significant persistent neutropenia (0.5-2.8 x 10³/µL; normal 1.9-8.0 x 10³/µL) was observed in one family with a specific GATA1 pathogenic variant [Hollanda et al 2006]; findings were variable in families with other GATA1 variants [Sankaran et al 2012, Zucker et al 2016].
  Note: Thrombocytopenia, anemia, and neutropenia are usually defined as two standard deviations below values observed in the normal population.
• Peripheral blood smear that may show the following:
  • Some platelets that are larger and more spherical than the typical discoid morphology. Platelets may be pale, reflecting reduced granularity.
  • Variation in erythrocyte size and shape and hypochromia, reflecting low hemoglobin content
  • Decreased neutrophils with abnormal morphology; this rare finding was reported in one family with an unusual germline pathogenic variant resulting in a truncated protein (GATA-1s; discussed in Molecular Genetics, Pathogenic variants) [Hollanda et al 2006].
• Bone marrow biopsy that may show the following:
  • Hyper- or hypocellularity
  • Increased or decreased numbers of megakaryocytes
  • Small, dysplastic megakaryocytes with signs of incomplete maturation
  • Dyserythropoiesis
  • Hypocellularity of erythroid and granulocytic lineages
  • Mild to moderate reticulin fibrosis [Åström et al 2015]
• Platelet function abnormalities. Defects in platelet aggregation in response to agonists (e.g., ristocetin, adenosine diphosphate, epinephrine, or collagen) occur in some cases [Thompson et al 1977, Freson et al 2001, Balduini et al 2004, Hollanda et al 2006]. These studies can be normal in some affected individuals.
• Electron microscopy. Findings in some cases include reduced numbers of platelet alpha granules and dysplastic features in megakaryocytes and platelets.
• In subtypes associated with globin chain imbalance, findings consistent with mild hemolysis, including mild reticulocytosis, elevated LDH, and low haptoglobin, may be present. In addition, HbA2 and HbF may be elevated.

Findings in heterozygous females. Females may manifest platelet abnormalities [White 2007] and mild to moderate symptoms such as menorrhagia or easy bruising, presumably related to the proportion of relevant cells that contain the pathogenic GATA1 variant on the active X chromosome [Nichols et al 2000; Raskind et al 2000; Balduini et al 2004; Del Vecchio et al 2005; Raskind, unpublished observations].

• Platelet counts may be normal or mildly to moderately decreased [Nichols et al 2000]; this may depend on the nature of the pathogenic variant or other (either genetic or environmental) modifiers.
• Morphologic abnormalities of platelets can be detected by electron microscopy [White 2007] and in some instances on peripheral blood smears [Tubman et al 2007].
• Two distinct platelet morphologies can be observed on peripheral blood smear, reflecting mosaicism secondary to random X-chromosome inactivation.

Course and prognosis. The long-term course in both males and females depends on disease severity:

• At the extreme end of the clinical spectrum, severe hemorrhage and/or erythrocyte transfusion dependence are life long.
• At the milder end, the risk for bleeding may spontaneously decrease with age, despite continued thrombocytopenia [Mehaffey et al 2001, Del Vecchio et al 2005].
• Some affected individuals may be recognized only after incidental findings of mild to moderate cytopenias on blood count analysis. These individuals have a good prognosis.

Genotype-Phenotype Correlations

Table 2 outlines the relationship between specific GATA1 pathogenic variants and associated phenotypic features.

For further information on murine and in vitro experiments involving GATA-1, see Molecular Genetics, Pathogenic variants.

Nomenclature

Until pathogenic variants in GATA1 were shown to underlie this heterogeneous disorder, a variety of terms were coined for the different clinical presentations. The first term used was X-linked thrombocytopenia with thalassemia (XLTT) [Raskind et al 2000]. Other terms used in the past and still in the current literature are "familial dyserythropoietic anemia and thrombocytopenia" [Nichols et al 2000, Del Vecchio et al 2005] and "X-linked macrothrombocytopenia" [Freson et al 2001].

To describe individuals with a clinical diagnosis of Diamond-Blackfan anemia in whom GATA1 pathogenic variants are identified and ribosomal protein variants are absent, the authors suggest the phrase "variant DBA associated with pathogenic variant of GATA1."

Prevalence

GATA1-related cytopenia is rare; the prevalence is not known. To date, hematopoietic disease caused by inherited pathogenic variants in GATA1 has been reported in 22 families [Nichols et al 2000, Freson et al 2001, Mehaffey et al 2001, Freson et al 2002, Yu et al 2002, Balduini et al 2004, Del Vecchio et al 2005, Hughan et al 2005, Phillips et al 2005, Hollanda et al 2006, Sankaran et al 2012, Singleton et al 2013, Hermans et al 2014, Klar et al 2014, Parrella et al 2014, Åström et al 2015, Di Pierro et al 2015, Zucker et al 2016].

GATA1 pathogenic variants may be more common than previously appreciated, particularly in persons with mild, unexplained thrombocytopenia/"gray platelet syndrome" present since birth [Tubman et al 2007] or individuals with congenital hypoplastic anemia/Diamond-Blackfan anemia with no ribosomal protein pathogenic variants [Sankaran et al 2012].

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed with GATA1-related cytopenia, the following are recommended:

• Complete blood count and examination of the peripheral smear to assess the degree of cytopenia(s)
• Detailed history of age at which hematologic disease was manifest
• Documentation of abnormal/unexpected bleeding episodes and platelet counts obtained at the time of the episodes to help determine whether platelet function is abnormal and whether disease severity has changed over time
  Note: Platelet aggregation studies may also be useful to identify functional abnormalities that predict a greater risk of bleeding for any given platelet count, but studies can be difficult to interpret when platelet counts are lower than 100,000/μL.
• Consultation with a clinical geneticist and/or genetic counselor

Treatment of Manifestations

Individuals with GATA1-related cytopenia are treated supportively.

Thrombocytopenia. Individuals with moderate to severe epistaxis, gingival bleeding, or gastrointestinal bleeding should receive platelet transfusions. Transfusion requirements vary from person to person as bleeding can be related to quantitative and/or qualitative platelet defects.

• For individuals with thrombocytopenia and/or platelet aggregation defects, DDAVP treatment may be helpful for short-term management of mild to moderate bleeding.
• Individuals who are only mildly symptomatic (easy bruisability without mucosal or more severe bleeding) do not require specific treatment.
• There is no evidence that splenectomy is beneficial in people with GATA1-related disease, although this treatment may be considered if splenomegaly is severe. Although splenectomy may improve the cytopenias, platelet dysfunction will not be improved.

Anemia. Erythrocyte transfusions are indicated when anemia is symptomatic (fatigue, tachycardia).

• Iron overload and the development of alloantibodies may limit chronic transfusion therapy.
• Extended pre-transfusion red blood cell phenotyping and matching for minor erythrocyte antigens in individuals receiving frequent transfusions can reduce the risk of alloimmunization.

Neutropenia. Individuals with neutropenia who present with fever should be evaluated