Diamond-Blackfan Anemia

Clinical characteristics.

Diamond-Blackfan anemia (DBA) in its classic form is characterized by a profound normochromic and usually macrocytic anemia with normal leukocytes and platelets, congenital malformations in up to 50% of affected individuals, and growth retardation in 30% of affected individuals. The hematologic complications occur in 90% of affected individuals during the first year of life. The phenotypic spectrum ranges from a mild form (e.g., mild anemia, no anemia with only subtle erythroid abnormalities, physical malformations without anemia) to a severe form of fetal anemia resulting in nonimmune hydrops fetalis. DBA is associated with an increased risk for acute myelogenous leukemia (AML), myelodysplastic syndrome (MDS), and solid tumors including osteogenic sarcoma.

Diagnosis/testing.

The diagnosis is established in a proband when all four of the following diagnostic criteria are present:

• Age younger than one year
• Macrocytic anemia with no other significant cytopenias
• Reticulocytopenia
• Normal marrow cellularity with a paucity of erythroid precursors

Other causes of bone marrow failure (e.g., Fanconi anemia, Pearson syndrome, dyskeratosis congenita, human immunodeficiency virus infection) need to be considered and ruled out as appropriate. DBA has been associated with pathogenic variants in 19 genes that encode ribosomal proteins and in GATA1 and TSR2. A pathogenic variant in one of these 21 genes is identified in approximately 65% of individuals with DBA.

Management.

Treatment of manifestations: Corticosteroid treatment, recommended in children older than age 12 months, initially improves the red blood cell count in approximately 80% of affected individuals. Chronic transfusion with packed red blood cells is initially necessary while the diagnosis is made and in those not responsive to corticosteroids. Hematopoietic stem cell transplantation (HSCT), the only curative therapy for the hematologic manifestations of DBA, is often recommended for those who are transfusion dependent or develop other cytopenias. Treatment of malignancies should be coordinated by an oncologist. Chemotherapy must be given cautiously as it may lead to prolonged cytopenia and subsequent toxicities.

Prevention of secondary complications: Transfusion-related iron overload is the most common complication in transfusion-dependent individuals. Iron chelation therapy with deferasirox orally or desferrioxamine subcutaneously is recommended after ten to 12 transfusions. Corticosteroid-related side effects must also be closely monitored, especially as related to risk for infection, growth retardation, and loss of bone density in growing children. Often individuals will be placed on transfusion therapy if these side effects are intolerable.

Surveillance: Complete blood counts several times a year; bone marrow aspirate/biopsy periodically to evaluate morphology and cellularity in the event of another cytopenia or a change in response to treatment. In steroid-dependent individuals: monitor blood pressure and (in children) growth.

Agents/circumstances to avoid: Deferiprone for the treatment of iron overload, which has led to severe neutropenia in a few individuals with DBA; infection (especially those on corticosteroids).

Evaluation of relatives at risk: Molecular genetic testing of at-risk relatives of a proband with a known pathogenic variant allows for early diagnosis and appropriate monitoring for bone marrow failure, physical abnormalities, and related cancers.

Genetic counseling.

DBA is most often inherited in an autosomal dominant manner; GATA1-related and TSR2-related DBA are inherited in an X-linked manner. Approximately 40% to 45% of individuals with autosomal dominant DBA have inherited the pathogenic variant from a parent; approximately 55% to 60% have a de novo pathogenic variant. Each child of an individual with autosomal dominant DBA has a 50% chance of inheriting the pathogenic variant. Males with GATA1- or TSR2-related DBA pass the pathogenic variant to all of their daughters and none of their sons. Women heterozygous for a GATA1 or TSR2 pathogenic variant have a 50% chance of transmitting the pathogenic variant in each pregnancy: males who inherit the pathogenic variant will be affected; females who inherit the pathogenic variant will be carriers and will usually not be affected. Carrier testing of at-risk female relatives is possible if the GATA1 or TSR2 pathogenic variant has been identified in the family. Prenatal testing for a pregnancy at increased risk is possible if the familial pathogenic variant has been identified.

Suggestive Findings

Diamond-Blackfan anemia (DBA) should be suspected in individuals with the following clinical, laboratory, and histopathologic features.

Clinical features

• Pallor, weakness, failure to thrive
• Growth retardation (observed in 30%)
• Congenital malformations (observed in ~30%-50%), in particular craniofacial, upper-limb, heart, and genitourinary malformations

Laboratory features

• Macrocytic anemia with no other significant cytopenias
• Increased red-cell mean corpuscular volume (MCV)
• Reticulocytopenia
• Elevated erythrocyte adenosine deaminase activity (eADA) (observed in 80%-85%)
• Elevated hemoglobin F (HbF) concentration

Histopathology features (bone marrow aspirate)

• Normal marrow cellularity
• Erythroid hypoplasia
• Marked reduction in normoblasts
• Persistence of pronormoblasts on occasion
• Normal myeloid precursors and megakaryocytes

Major supporting diagnostic criteria of classic DBA

• Identification of a pathogenic variant in one of the genes known to be associated with DBA (see Table 1a and Table 1b)
• Family history of DBA consistent with autosomal dominant inheritance

Minor supporting diagnostic criteria of classic DBA

• Elevated eADA
• Elevated HbF concentration
• One or more congenital anomalies described in classic DBA
• No evidence of another inherited disorder of bone marrow function (see Differential Diagnosis)

Features of non-classic DBA

• Mild or absent anemia with only subtle indications of erythroid abnormalities such as macrocytosis, elevated eADA, and/or elevated HbF concentration
• Onset later in life [Lipton et al 2006]
• Congenital anomalies or short stature consistent with DBA and minimal or no evidence of abnormal erythropoiesis [Lipton & Ellis 2010]

Establishing the Diagnosis

To establish the diagnosis in a proband the following tests should be performed:

• Complete blood count with reticulocyte count
• Erythrocyte adenosine deaminase activity
• Fetal hemoglobin
• Bone marrow aspiration and biopsy

The diagnosis of DBA is established in a proband when all four of the following diagnostic criteria are met [Vlachos et al 2008, Vlachos & Muir 2010]:

• Age younger than one year
• Macrocytic anemia with no other significant cytopenias
• Reticulocytopenia
• Normal marrow cellularity with a paucity of erythroid precursors

Note: The following diagnoses should be considered in individuals with a suspected diagnosis of DBA who do not meet all four of the diagnostic criteria and do not have a pathogenic variant in one of the genes listed in Table 1a or Table 1b [Vlachos & Muir 2010]. See Differential Diagnosis.

• Fanconi anemia
• Pearson syndrome
• Dyskeratosis congenita
• Human immunodeficiency virus (HIV)
• Transient erythroblastopenia of childhood
• Shwachman-Diamond syndrome
• Parvovirus B19
• Other infections
• Drugs and toxins
• Immune-mediated diseases

Molecular testing for identification of a heterozygous pathogenic variant in one of the genes listed in Table 1a or Table 1b establishes the diagnosis of DBA if clinical features are inconclusive.

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

Serial single-gene testing

1.

Sequence analysis of RPS19 is performed first.

2.

If no pathogenic variant in RPS19 is found, perform sequence analysis of the remaining 20 genes in which pathogenic variants are known to cause DBA (see Table 1a and Table 1b).

3.

If sequence analysis does not reveal a pathogenic variant, deletion/duplication analysis should be performed for the genes in which a deletion/duplication has been previously identified (see Table 1a).

A multigene panel that includes the genes in Table 1a and Table 1b and other genes of interest (see Differential Diagnosis) may also 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, genome sequencing, and mitochondrial sequencing may be considered if serial single-gene testing (and/or use of a multigene panel) fails to confirm a diagnosis in an individual with features of DBA.

For an introduction to comprehensive genomic testing click here. More detailed information for clinicians ordering genomic testing can be found here.

See Table 1a for the most common genetic causes (i.e., pathogenic variants of any one of the genes included in this table account for ≥1% of DBA) and Table 1b for less common genetic causes (i.e., pathogenic variants of any one of the genes included in this table are reported in only a few families).

Clinical Description

Anemia. The primary hematologic feature of Diamond-Blackfan anemia (DBA) is a profound isolated normochromic and usually macrocytic anemia with normal leukocytes and platelets [Alter & Young 1998, Dianzani et al 2000]. The hematologic complications of DBA occur in 90% of affected individuals during the first year of life: the median age at presentation is two months and the median age at diagnosis is three months [Bagby et al 2004, Ohga et al 2004]. Treatment with corticosteroids is recommended in children older than age 12 months [Vlachos & Muir 2010] (see Management). Eventually, 40% of affected individuals are steroid dependent, 40% are transfusion dependent, and 20% go into remission [Chen et al 2005, Vlachos et al 2008].

Congenital malformations are observed in approximately 50% of affected individuals and more than one anomaly is observed in up to 25% of individuals. The most commonly reported abnormalities (and their reported frequency) include the following [Bagby et al 2004, Lipton et al 2006, Vlachos et al 2008, Vlachos & Muir 2010]:

• Head and face (50%). Microcephaly; hypertelorism, epicanthus, ptosis; microtia, low-set ears; broad, depressed nasal bridge; cleft lip/palate, high arched palate; micrognathia; low anterior hairline
• Eye. Congenital glaucoma, congenital cataract, strabismus
• Neck. Webbing, short neck, Klippel-Feil anomaly, Sprengel deformity
• Upper limb and hand including thumb (38%). Absent radial artery; flat thenar eminence; triphalangeal, duplex, bifid, hypoplastic, or absent thumb
• Genitourinary (19%). Absent kidney, horseshoe kidney; hypospadias
• Heart (15%). Ventricular septal defect, atrial septal defect, coarctation of the aorta, other cardiac anomalies
• Growth. Low birth weight was reported in 25% of affected infants. Thirty percent of affected individuals have growth retardation. Growth retardation can be influenced by other factors including steroid treatment [Chen et al 2005, Vlachos et al 2008].
• Malignancy. DBA is associated with an increased risk for acute myelogenous leukemia (AML), myelodysplastic syndrome (MDS), and solid tumors including osteogenic sarcoma [Janov et al 1996, Vlachos et al 2001, Vlachos et al 2012].
• Development. Rarely, in children with DBA developmental delay can occur [Willig et al 1999, Tentler et al 2000, Farrar et al 2011, Kuramitsu et al 2012].

The phenotypic spectrum of DBA is broad. Within the same family, some affected individuals may have classic disease, whereas others may have a non-classic form including (1) mild anemia; (2) no anemia with only subtle erythroid abnormalities such as macrocytosis, elevated erythrocyte adenosine deaminase activity (eADA), and/or increased HbF concentration; or (3) physical malformations without anemia. Others may have a severe form presenting with fetal anemia that results in nonimmune hydrops fetalis [Dunbar et al 2003, Saladi et al 2004]. Onset of non-classic DBA can be later than age one year.

Genotype-Phenotype Correlations

RPL5. Craniofacial, congenital heart, and thumb defects were more severe than those seen with pathogenic variants in RPL11 and RPS19 [Gazda et al 2008, Quarello et al 2010]. Cleft lip and/or cleft palate (CL/P) was reported in 45% of affected persons with RPL5 pathogenic variants [Gazda et al 2008] and in 50% of an affected group of Italians with RPL5 pathogenic variants [Quarello et al 2010]. Small gestational age was reported in seven of eight individuals with an RPL5 pathogenic variant versus 43% of individuals with an RPS19 pathogenic variant [Cmejla et al 2009]. None of the eight individuals with an RPL5 pathogenic variant had CL/P.

RPL11. Pathogenic variants in RPL11 are predominantly associated with thumb abnormalities [Gazda et al 2008, Cmejla et al 2009]. In the Italian group with DBA, two persons with RPL11 pathogenic variants were identified with CL/P [Quarello et al 2010].

GATA1. The splice site variants IVS2+1delG and 220G>C (p.Leu74Val) affecting GATA1 exon 2 cause DBA with profound anemia.

RPS10, RPS19, RPS26. No genotype-phenotype correlations were found in persons with pathogenic variants in RPS10, RPS19, and RPS26 [Willig et al 1999, Cmejla et al 2000, Ramenghi et al 2000, Orfali et al 2004, Doherty et al 2010].

RPS29. To date, no genotype-phenotype correlations have been identified in persons with RPS29 pathogenic variants.

RPL27, RPL31, RPS27. To date, no genotype-phenotype correlations have been identified in persons with RPL27, RPL31, or RPS27 pathogenic variants.

RPS28. Two families with DBA with mandibulofacial dystostosis were described [Gripp et al 2014].

TSR2. One family with DBA with mandibulofacial dystostosis was described [Gripp et al 2014].

Penetrance

Penetrance is incomplete.

Nomenclature

DBA has previously been known as congenital hypoplastic anemia of Blackfan and Diamond, congenital hypoplastic anemia, Blackfan-Diamond syndrome, Aase syndrome, and Aase-Smith syndrome II.

Prevalence

The incidence of DBA is estimated at between 1:100,000 and 1:200,000 live births; it remains consistent across ethnicities [Vlachos et al 2008].

Transient Erythroblastopenia of Childhood

Transient erythroblastopenia of childhood (TEC) (OMIM 227050) is characterized by acquired anemia caused by decreased production of red blood cell precursors in a previously healthy child. The etiology of TEC is unknown, although an association with viral infections has been proposed. TEC is almost always self-resolving within one to several months and only requires clinical intervention (e.g., red blood cell transfusion) in severe cases [Alter & Young 1998].

TEC can be distinguished from DBA because in TEC:

• More than 80% of children are age one year or older at diagnosis, whereas in DBA, 90% of children are younger than age one year at the time of diagnosis [Alter & Young 1998];
• Only 10% of children have elevated eADA, compared to approximately 85% of individuals with DBA [Glader & Backer 1988, Vlachos et al 2008];
• Anemia is normocytic, whereas in DBA it is macrocytic [Alter & Young 1998].

Other Genetic Conditions with Bone Marrow Failure

Fanconi anemia (FA) is characterized by physical abnormalities, bone marrow failure (BMF), and increased risk for malignancy. Physical abnormalities, present in 60%-75% of affected individuals, include short stature; abnormal skin pigmentation; malformations of the thumbs, forearms, skeletal system, eyes, kidneys and urinary tract, ear, heart, gastrointestinal system, oral cavity, and central nervous system; hearing loss; hypogonadism; and developmental delay. Progressive BMF with pancytopenia typically presents in the first decade, often initially with thrombocytopenia or leukopenia. By age 40 to 48 years, the estimated cumulative incidence of BMF is 90%; the incidence of hematologic malignancies (primarily acute myeloid leukemia) is 10%-33%; and of non-hematologic malignancies (solid tumors, particularly of the head and neck, skin, GI tract, and genital tract) 25%-30%.

The diagnosis of FA rests on the detection of chromosome aberrations (breaks, rearrangements, radials, exchanges) in cells after culture with a DNA interstrand cross-linking agent such as diepoxybutane (DEB) or mitomycin C (MMC). Molecular genetic testing is complicated by the presence of at least 18 genes, which are responsible for the FA complementation groups including [A, B, C, D1 (BRCA2), D2, E, F, G, I, J (BRIP1), L, M, and N (PALB2), O (RAD51C), and P (SLX4)].

FANCB-related FA is inherited in an X-linked manner. All other types of FA are inherited in an autosomal recessive manner.

Shwachman-Diamond syndrome (SDS) is characterized by exocrine pancreatic dysfunction with malabsorption, malnutrition, and growth failure; hematologic abnormalities with single- or multi-lineage cytopenias and susceptibility to myelodysplasia syndrome (MDS) and acute myelogenous leukemia (AML); and bone abnormalities. In almost all affected children, persistent or intermittent neutropenia is a common presenting finding, often before the diagnosis of SDS is made. Short stature and recurrent infections are common.

The diagnosis of SDS relies on clinical findings, including pancreatic dysfunction and characteristic hematologic problems. SDS is caused by mutation of SBDS and inherited in an autosomal recessive manner.

Pearson syndrome is characterized by sideroblastic anemia of childhood, pancytopenia, exocrine pancreatic failure, and renal tubular defects. Progressive liver failure and intractable metabolic acidosis typically result in death in infancy. Those who survive develop neurologic symptoms. Pearson syndrome is most often caused by de novo deletions in mitochondrial DNA (mtDNA), but rearrangements (large-scale partial deletions and duplications) have been found [Morel et al 2009]. Inheritance is maternal (see Mitochondrial DNA Deletion Syndromes).

Dyskeratosis congenita (DC), a telomere biology disorder, is characterized by a classic triad of dysplastic nails, lacy reticular pigmentation of the upper chest and/or neck, and oral leukoplakia. People with DC are at increased risk for progressive BMF, MDS or AML, solid tumors (usually squamous cell carcinoma of the head/neck or anogenital cancer), and pulmonary fibrosis. Onset and progression of manifestations of DC vary: at the mild end of the spectrum are those who have only minimal physical findings with normal bone marrow function, and at the severe end are those who have the diagnostic triad and early-onset BMF. Treatment for DC includes androgen therapy and possible bone marrow transplantation [Alter & Young 1998, Alter 2007]. DC can be inherited in an X-linked, autosomal recessive, or autosomal dominant manner.

Cartilage-hair hypoplasia (CHH) is characterized by the presence of short tubular bones at birth and variable other findings including fine sparse blond hair; anemia; macrocytosis with or without anemia; and defective T-cell-mediated responses resulting in severe immunodeficiency. The incidence is highest in the Amish and Finnish populations. Treatment includes red blood cell transfusions and steroid therapy [Alter & Young 1998, Hermanns et al 2005]. CHH is caused by mutation of RMRP and is inherited in an autosomal recessive manner.

Acquired Conditions with BMF

Infections

• Parvovirus B19 infection; usually asymptomatic, but occasionally can cause red cell aplasia, which is most often mild and self-limited by production of virus-neutralizing antibodies in the host [Parekh et al 2005]. However, in persons with hereditary or acquired anemia, parvovirus infection can be severe and life-threatening, requiring red blood cell transfusions. Seropositivity for parvovirus reaches 50% by age 15 years and 90% in the elderly.
• HIV; associated with pure red cell aplasia (PRCA) [Alter & Young 1998]
• Viral hepatitis
• Mononucleosis and human T-cell lymphotropic virus type 1 [Alter & Young 1998]

Drugs and toxins

• Antiepileptic drugs: diphenylhydantoin, sodium valproate, carbamazepine, sodium dipropylacetate
• Others: azathioprine; chloramphenicol and thiamphenicol; sulfonamides; isoniazid; procainamide [Alter & Young 1998]

Immune-mediated diseases

• Thymoma, most commonly associated with PRCA. Approximately 5%-10% of persons with thymoma develop PRCA.
• Myasthenia gravis, systemic lupus erythematosus, and multiple endocrinopathies [Alter & Young 1998]

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed with Diamond-Blackfan anemia (DBA), the following are recommended:

• Evaluation by a hematologist
• Evaluation by a clinical geneticist for congenital malformations and to obtain a detailed family history
• Ophthalmology evaluation for glaucoma and cataract for individuals on steroid therapy
• Orthopedic evaluation for individuals with clinical findings suggestive of Klippel-Feil anomaly or Sprengel deformity
• Orthopedic evaluation for individuals with upper-limb and/or thumb anomalies
• Ultrasound examination of the kidney and urinary tract
• Evaluation by a nephrologist and a urologist, as appropriate
• Evaluation by a cardiologist including echocardiography
• Developmental assessment

Treatment of Manifestations

Eventually, 40% of individuals are steroid dependent, 40% are transfusion dependent, and 20% go into remission [Chen et al 2005, Vlachos et al 2008].

Corticosteroid administration. Corticosteroids can initially improve the red blood count in approximately 80% of affected individuals.

• The recommended corticosteroid is prednisone with a starting dose of 2 mg/kg/day given orally once a day in the morning, beginning after age 12 months. An increase in hemoglobin concentration is usually seen in two to four weeks.
• Corticosteroids may be slowly tapered to the minimal effective dose. Monitoring of blood counts is needed to ensure that the red cell hemoglobin concentration remains at 80-100 g/L, the minimum required for transfusion independence.
• The corticosteroid maintenance dose varies and can be extremely low in some individuals. The recommended maximum maintenance dose is ≤0.5 mg/kg/day or ≤1 mg/kg every other day.
• If after approximately one month the recommended steroid dose does not sustain the red cell hemoglobin concentration in an acceptable range, the corticosteroids should be tapered and discontinued.

Side effects of corticosteroids include osteoporosis, weight gain, cushingoid appearance, hypertension, diabetes mellitus, growth retardation, pathologic bone fractures, gastric ulcers, cataracts, glaucoma, and increased susceptibility to infection [Alter & Young 1998, Willig et al 1999, Lipton et al 2006].

Red blood cell transfusion. If the individual is resistant to corticosteroid therapy, chronic transfusion with packed red blood cells is necessary. The goal of transfusion therapy is a red cell hemoglobin concentration of 80-100 g/L, which is usually adequate for maintaining growth and development [Vlachos et al 2008, Vlachos & Muir 2010].

Hematopoietic stem cell transplantation (HSCT) is the only curative therapy for DBA. Persons with DBA who are transfusion dependent or develop other cytopenias are often treated with HSCT.

In one study of 61 persons with DBA who underwent bone marrow transplantation (BMT), the majority (67%) received their bone marrow grafts from an HLA-matched related donor. The three-year probability of overall survival was 64% (range 50%-74%). Transplantation from an HLA-identical sib donor was associated with better survival [Roy et al 2005].

The Diamond-Blackfan Anemia Registry of North America describes 36 individuals who underwent HSCT: 21 HLA-matched sib stem cell transplants and 15 alternative donor stem cell transplants. Survival greater than five years from SCT for allogeneic sib transplants was 72.7% ±10.7% versus survival greater than five years from alternative donor transplants of 17.1% ±11.9% [Lipton et al 2006, Vlachos et al 2008]. Survival was the best (92.3%) for children younger than age ten years transplanted using an HLA-matched sib.

Note: (1) It is recommended that the affected individual, sibs, and parents undergo HLA typing at the time of diagnosis of DBA to identify the most suitable bone marrow donor in the event that HSCT would be required. (2) Because penetrance of DBA is incomplete, it is possible that a relative considered as a bone marrow donor could have a pathogenic variant but not manifest findings of DBA. (3) Relatives with a pathogenic variant, regardless of their clinical status, are not suitable bone marrow donors, because their donated bone marrow may fail or not engraft