Summary
Clinical characteristics.
Diamond-Blackfan anemia (DBA) is characterized by a profound normochromic and usually macrocytic anemia with normal leukocytes and platelets, congenital malformations in up to 50%, and growth deficiency 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 or 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 clinical diagnosis can be established in a proband with macrocytic anemia with onset prior to age one year, no other significant cytopenias, reticulocytopenia, normal marrow cellularity with a paucity of erythroid precursors, and no evidence of another acquired or inherited disorder of bone marrow function.
The molecular diagnosis can be established in a female proband by identification of a heterozygous pathogenic variant in one of the 22 genes associated with DBA.
The molecular diagnosis can be established in a male proband by identification of a heterozygous pathogenic variant in a gene associated with autosomal dominant DBA or identification of a hemizygous pathogenic variant in GATA1 or TSR2 (associated with X-linked inheritance).
Management.
Treatment of manifestations: Corticosteroid treatment, recommended in children older than age 12 months, improves the red blood cell count in approximately 80% of affected individuals. Chronic transfusion with packed red blood cells is necessary during the first year of life to avoid steroid-induced toxicity in those not responsive to a trial of corticosteroids at age 12 months and in individuals who relapse. Hematopoietic stem cell transplantation, the only curative therapy for the hematologic manifestations of DBA, is often recommended for those who are transfusion dependent or develop other cytopenias. Ocular, skeletal, genitourinary, cardiac, and endocrine complications are best managed in collaboration with appropriate subspecialists. 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 deficiency, 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 to evaluate morphology and cellularity only in the event of another cytopenia or a change in response to treatment. In steroid-dependent individuals: monitor blood pressure and (in children) growth. Evaluation by an endocrinologist for those who are steroid dependent and those at risk for transfusion iron overload. Cancer surveillance includes history, physical examination, and blood counts every four to six months. If red blood cell, white blood cell, or platelet counts fall rapidly, bone marrow aspirate with biopsy and cytogenetic studies (including karyotype and FISH analysis) to look for acquired abnormalities in chromosomes 5, 7, and 8 that are associated with myelodysplastic syndrome or leukemia.
Agents/circumstances to avoid: Deferiprone for the treatment of iron overload (which can cause neutropenia); infection (especially in individuals 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.
Pregnancy management: Management by an obstetrician with expertise in high-risk pregnancies and hematologists with experience in bone marrow failure syndromes. During pregnancy the maternal hemoglobin level must be monitored. Use of low-dose aspirin up to 37 weeks' gestation may help prevent vasculo-placental complications in women with a history of a problematic pregnancy.
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.
Autosomal dominant. Approximately 40%-45% of individuals with autosomal dominant DBA have inherited the pathogenic variant from a parent; approximately 55%-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.
X-linked. 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.
Once the DBA-causing pathogenic variant has been identified in an affected family member, prenatal testing for a pregnancy at increased risk and preimplantation genetic testing are possible.
Diagnosis
Suggestive Findings
Diamond-Blackfan anemia (DBA) should be suspected in individuals with the following clinical, laboratory, and histopathologic features, and no evidence of another inherited disorder of bone marrow function.
Clinical features
Pallor, weakness, failure to thrive
Growth deficiency (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 erythrocyte mean corpuscular volume
Reticulocytopenia
Elevated erythrocyte adenosine deaminase activity (eADA) (observed in 80%-85%)
Elevated hemoglobin F 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
Other. Individuals show no evidence of another inherited disorder of bone marrow function. See Differential Diagnosis.
Establishing the Diagnosis
The clinical diagnosis of DBA can be established in a proband with all of the following clinical, laboratory, and histopathology features:
Macrocytic anemia with onset prior to age one year
No other significant cytopenias
Reticulocytopenia
Normal marrow cellularity with a paucity of erythroid precursors
The molecular diagnosis can be established in a female proband by identification of a heterozygous pathogenic (or likely pathogenic) variant in one of the genes listed in Table 1.
The molecular diagnosis can be established in a male proband by identification of a heterozygous pathogenic (or likely pathogenic) variant in one of the genes listed in Table 1 associated with autosomal dominant inheritance, or a hemizygous pathogenic (or likely pathogenic) variant in GATA1 or TSR2 associated with X-linked inheritance.
Note: (1) Per ACMG/AMP variant interpretation guidelines, the terms "pathogenic variants" and "likely pathogenic variants" are synonymous in a clinical setting, meaning that both are considered diagnostic and both can be used for clinical decision making [Richards et al 2015]. Reference to "pathogenic variants" in this section is understood to include any likely pathogenic variants. (2) The identification of variant(s) of uncertain significance cannot be used to confirm or rule out the diagnosis.
Molecular testing approaches usually begin with a multigene panel with analysis of DBA-related genes (rare DBA-related genes may not be included in a panel). Failure to identify a gene can be followed by more comprehensive
genomic testing [Ulirsch et al 2018].
Table 1.
Molecular Genetic Testing Used in Diamond-Blackfan Anemia (DBA)
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Gene 1,2 | Proportion of DBA Attributed to Pathogenic Variants in Gene | Proportion of Probands with a Pathogenic Variant 3 Detected by Method |
---|
Sequence analysis 4,5 | Gene-targeted deletion/duplication analysis 5,6 |
---|
GATA1 7 | <1% (5 families) | ~100% | None reported |
RPL5
| 7%-12% | ~95% | <5% |
RPL9
| <1% | ~100% | None reported |
RPL11
| 5%-7% | ~90% | ~10% |
RPL15
| ~1% | ~80% | ~20% |
RPL18
| Rare | 1 family | None reported |
RPL26
| Rare | 1 person | None reported |
RPL27
| Rare | 2 persons | None reported |
RPL31
| Rare | 1 person | 1 person |
RPL35
| Rare | 1 family | 2 persons |
RPL35A
| 2%-3% | ~50% | ~50% |
RPS7
| ~1% | ~100% | None reported |
RPS10
| 1%-3% | ~100% | None reported |
RPS15A
| Rare | 1 family | None reported |
RPS17
| 1%-3% | <35% | >65% |
RPS19
| 25%-30% | ~95% | ~5% |
RPS24
| 2%-3% | ~90% | 1 person |
RPS26
| 6.6%-9% | >80% | <20% |
RPS27
| Rare | 1 person | None reported |
RPS28
| Rare (2 families) | 2 families | None reported |
RPS29
| ~1% | ~80% | 1 person |
TSR2
| Rare | 1 family | None reported |
Unknown | ~20% | NA | |
Pathogenic variants of any one of the genes included in this table account for ≥1% of DBA.
- 1.
Genes are listed in alphabetic order.
- 2.
- 3.
- 4.
Sequence analysis detects variants that are benign, likely benign, of uncertain significance, likely pathogenic, or pathogenic. Variants may include small intragenic deletions/insertions and missense, nonsense, and splice site variants; typically, exon or whole-gene deletions/duplications are not detected. For issues to consider in interpretation of sequence analysis results, click here.
- 5.
Data derived from the subscription-based professional view of Human Gene Mutation Database [Stenson et al 2020]
- 6.
Gene-targeted deletion/duplication analysis detects intragenic deletions or duplications. Methods used may include a range of techniques such as quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and a gene-targeted microarray designed to detect single-exon deletions or duplications.
- 7.
There is not consensus as to whether individuals with a GATA1 pathogenic variant associated with overlapping clinical features of DBA should be diagnosed with GATA1-related cytopenia or DBA.
Clinical Characteristics
Clinical Description
Diamond-Blackfan anemia (DBA) is characterized by early-onset hypoplastic anemia. Congenital anomalies are observed in approximately 50% of affected individuals and more than one anomaly is observed in up to 25% of individuals. Additional features include growth deficiency and predisposition to malignancy.
Table 2.
Diamond-Blackfan Anemia: Frequency of Select Features
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Feature | % of Persons with Feature 1 | Comment |
---|
Anemia
| 100% | 90% in 1st year of life |
Craniofacial features
| 27% | |
Upper limb anomalies
| 16% | |
Genitourinary malformations
| 13% | |
Heart defects
| 11% | |
Growth deficiency
| 30% | |
Malignancy
| 2%-5% | Acute myelogenous leukemia, myelodysplastic syndrome, & solid tumors incl osteogenic sarcoma & lung, colon, & cervical carcinomas |
Anemia. The primary hematologic feature of DBA is a profound normochromic, macrocytic anemia with normal leukocytes and platelets. 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 (see Management). Approximately 70% of individuals respond but eventually 40% remain steroid dependent and 40% become transfusion dependent; 20% go into remission [Chen et al 2005, Vlachos et al 2008].
Craniofacial features include microcephaly; hypertelorism, epicanthus, ptosis; microtia, low-set ears; broad, depressed nasal bridge; cleft lip/palate, high arched palate; micrognathia; low anterior hairline.
Eye findings include congenital glaucoma, congenital cataract, strabismus.
Neck. Features include webbing, short neck, Klippel-Feil anomaly, Sprengel deformity.
Upper limb and hand including thumb. Findings include absent radial artery; flat thenar eminence; triphalangeal, duplex, bifid, hypoplastic, or absent thumb.
Genitourinary findings include absent kidney, horseshoe kidney; hypospadias.
Heart findings include ventricular septal defect, atrial septal defect, coarctation of the aorta, other cardiac anomalies.
Growth deficiency. Low birth weight was reported in 25% of affected infants. Thirty percent of affected individuals have growth deficiency. Growth deficiency 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, myelodysplastic syndrome, and solid tumors including osteogenic sarcoma [Janov et al 1996, Vlachos et al 2001, Vlachos et al 2012, Alter et al 2018].
Development. Rarely, developmental delay can occur [Kuramitsu et al 2012].
The phenotypic spectrum is broad. Within the same family, affected individuals can have typical DBA or atypical phenotypes including (1) mild anemia; (2) no anemia with only subtle erythroid abnormalities such as macrocytosis, elevated erythrocyte adenosine deaminase activity, and/or increased hemoglobin F 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 atypical DBA can be later than age one year.
Phenotype Correlations by Gene
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 (~88%) of eight individuals with an RPL5 pathogenic variant versus 43% of individuals with an RPS19 pathogenic variant [Cmejla et al 2009].
RPL11. Pathogenic variants in RPL11 are predominantly associated with thumb abnormalities [Gazda et al 2008, Cmejla et al 2009].
Genotype-Phenotype Correlations
Many pathogenic variants are unique to a family and no genotype-phenotype correlations have been confirmed.
Penetrance
Penetrance is almost complete with loss-of-function variants in RPL5, RPS19, and RPS26. Penetrance is high with loss-of-function variants in other genes that encode ribosomal subunits. Missense variants (e.g., of RPS19) appear to be less penetrant [Ulirsch et al 2018].
Nomenclature
Diamond-Blackfan anemia 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; incidence remains consistent across ethnicities [Vlachos et al 2008].
Management
Evaluations Following Initial Diagnosis
To establish the extent of disease and needs in an individual diagnosed with Diamond-Blackfan anemia (DBA), the evaluations summarized in Table 4 (if not performed as part of the evaluation that led to the diagnosis) are recommended.
Table 4.
Recommended Evaluations Following Initial Diagnosis in Individuals with Diamond-Blackfan Anemia
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System/Concern | Evaluation | Comment |
---|
Anemia
| Eval by hematologist for macrocytosis & reticulocytopenia | Macrocytosis is not always present. |
Congenital
anomalies
| Eval by clinical geneticist for congenital malformations | |
Eyes
| Ophthalmology eval for glaucoma & cataract for persons on steroid therapy | |
Skeletal
anomalies
| Orthopedic eval for persons w/:
| |
Genitourinary
anomalies
|
| |
Cardiology
| Eval by cardiologist incl echocardiography | |
Endocrine
| Growth assessment | |
Development
| Developmental assessment | |
Genetic
counseling
| By genetics professionals 1 | To inform affected persons & their families re nature, MOI, & implications of DBA in order to facilitate medical & personal decision making |
Family support
& resources
| Assess need for:
| |
DBA = Diamond-Blackfan anemia; MOI = mode of inheritance
- 1.
Medical geneticist, certified genetic counselor, certified advanced genetic nurse
Treatment of Manifestations
Anemia. 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 and ten days to two weeks after a transfusion. An increase in hemoglobin and reticulocyte count is usually seen in two to four weeks. If there is no response by three weeks, steroids can be tapered over two 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. Concerns about the long-term effects of steroids have led to the recommendation of 0.25 mg/kg/day as a preferable maximum daily dose.
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 restriction, pathologic bone fractures, gastric ulcers, cataracts, glaucoma, and increased susceptibility to infection.
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.
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 HSCTs and 15 alternative donor HSCTs. Survival greater than five years from HSCT 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.
In a French/German HSCT study of 70 children with DBA, a matched sib donor was available for 45 individuals, a 10/10 HLA matched unrelated donor in 12 individuals, a 9/10 HLA matched unrelated donor in seven individuals, and a less compatible or incomplete HLA matched donor in six individuals. Overall survival was 91% with no difference by donor type. All individuals engrafted; one individual had secondary graft failure. The difference in chronic GVHD between children transplanted before age ten years compared with older individuals did not reach statistical significance.
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 in the recipient.
Treatment of other manifestations
Glaucoma and cataract. As recommended by ophthalmologist
Skeletal anomalies. Surgical management of thumb anomalies as recommended by orthopedist; occupational and physical therapy as needed
Genitourinary malformations. Managed as recommended by nephrologist and/or urologist
Congenital heart defects. As recommended by cardiologist
Cancer. Treatment of malignancies coordinated by oncologist
Prevention of Secondary Complications
Transfusion iron overload is the most common complication in transfusion-dependent individuals. The following methods are used both to assess for evidence of transfusion iron overload and to evaluate the effectiveness of iron chelation therapy:
Measurement of iron concentration in a liver biopsy specimen, which accurately determines total body iron accumulation
T2*-weighted MRI for assessing iron loading in the liver and heart
Magnetic biosusceptometry (SQUID), which gives a measurement of hepatic iron concentration
Note: (1) Although the latter two methods of total iron measurement are noninvasive, SQUID is not widely available. MRI is now more widely available and referral to a center with experience in this technique is advisable to obtain a baseline measurement and to more conveniently follow progress after starting chelation therapy. Although liver biopsy is the "gold standard" [Cappellini & Piga 2008, Vlachos et al 2008] it is not a practical choice for long-term follow up. (2) Routine measurement of serum ferritin concentration is not reliable in detecting iron overload because the serum ferritin concentration does not always correlate with total body iron accumulation.
Iron chelation therapy is usually started after ten to 12 transfusions (170-200 mL/kg of packed red blood cells), when serum ferritin concentration reaches 1,000-1,500 µg/L, or when hepatic iron concentration reaches 6-7 mg/g of dry weight liver tissue.
Deferasirox is recommended in individuals age two years or older. It is administered once daily in an oral dose of 20-30 mg/kg/day. Side effects are usually mild and include rash, nausea, creatinine elevation, and rarely proteinuria and transaminase elevation. In affected individuals, satisfaction with deferasirox is greater than with desferrioxamine, mostly because of ease of administration [
Cappellini & Piga 2008,
Porter et al 2008,
Vlachos et al 2008].
Desferrioxamine is administered four to seven nights a week in an eight- to 12-hour subcutaneous infusion via a portable pump. The recommended initial dose is 40 mg/kg/day; the maximum dose is 50-60 mg/kg/day. The dose and frequency of infusion may be modified using the serum ferritin concentration or the hepatic iron concentration as a guide [
Cappellini & Piga 2008,
Vlachos et al 2008]. Side effects include ocular and auditory toxicity and growth deficiency. Compliance rate is hampered by the demanding administration route and schedule.
Note: Deferiprone is not recommended in the treatment of iron overload in individuals with DBA [Vlachos et al 2008] because its side effects include neutropenia [Henter & Karlen 2007].
Side effects of corticosteroids include osteoporosis, weight gain, cushingoid appearance, hypertension, diabetes mellitus, growth deficiency, pathologic bone fractures, gastric ulcers, cataracts, glaucoma, and increased susceptibility to infection [Alter & Young 1998, Willig et al 1999, Lipton et al 2006].
One of the critical side effects of corticosteroids is growth deficiency. If growth is severely impaired, corticosteroids should be stopped and replaced by a short-term red blood cell transfusion regimen [Vlachos et al 2008].
Surveillance
The following are indicated:
Complete blood counts several times a year
Bone marrow aspirate/biopsy to evaluate morphology and cellularity, if evidence of another cytopenia or failure of current treatment is noted
Monitoring of blood pressure in individuals who are steroid dependent
Monitoring of growth in individuals who are steroid dependent and in those at risk for transfusion iron overload
Evaluation by an endocrinologist; recommended for individuals who are steroid dependent and those at risk for transfusion iron overload
Cancer surveillance includes the following:
In individuals with DBA who are otherwise healthy, every four to six months: an interim history, physical examination, and measurement of blood count
If red blood cell, white blood cell, or platelet counts fall rapidly, bone marrow aspirate with biopsy and cytogenetic studies (including karyotype and FISH analysis) to look for acquired abnormalities in chromosomes 5, 7, and 8 that are associated with certain cancers [
Vlachos et al 2008]
Agents/Circumstances to Avoid
Deferiprone is not recommended in the treatment of iron overload in persons with DBA because its side effects include neutropenia [Vlachos et al 2008].
Individuals with DBA, especially those on corticosteroid treatment, should take reasonable precautions to avoid infections, as steroid-dependent individuals are more prone to complications resulting from immune system dysfunction.
Evaluation of Relatives at Risk
It is appropriate to evaluate apparently asymptomatic older and younger at-risk relatives of an affected individual to allow early diagnosis and appropriate monitoring for bone marrow failure, physical abnormalities, and related cancers. Evaluations include:
See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.
Pregnancy Management
Management of pregnancy in women with DBA requires obstetricians with expertise in high-risk pregnancies and hematologists with experience with bone marrow failure syndromes [Alter et al 1999, Taher et al 2020].
During pregnancy the maternal hemoglobin level must be monitored.
Use of low-dose aspirin up to 37 weeks' gestation may help prevent vasculo-placental complications in women with a history of a previous problematic pregnancy [Faivre et al 2006].
A study that surveyed 64 pregnancies in women with DBA found a high incidence of complications in both mothers and children. Risks include the following [Faivre et al 2006]:
Therapies Under Investigation
Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.
Genetic Counseling
Genetic counseling is the process of providing individuals and families with
information on the nature, mode(s) of inheritance, and implications of genetic disorders to help them
make informed medical and personal decisions. The following section deals with genetic
risk assessment and the use of family history and genetic testing to clarify genetic
status for family members; it is not meant to address all personal, cultural, or
ethical issues that may arise or to substitute for consultation with a genetics
professional. —ED.
Mode of Inheritance
Most often, Diamond-Blackfan anemia (DBA) is inherited in an autosomal dominant manner. GATA1-related DBA and TSR2-related DBA are inherited in an X-linked manner.
Autosomal Dominant Inheritance – Risk to Family Members
Parents of a proband
Approximately 40%-45% of individuals diagnosed with autosomal dominant DBA inherited a DBA-causing pathogenic variant from a parent who may or may not have manifestations of DBA [
Orfali et al 2004].
Approximately 55%-60% of individuals diagnosed with autosomal dominant DBA have the disorder as the result of a de novo pathogenic variant.
If the proband appears to be the only affected family member (i.e., a simplex case), molecular genetic testing is recommended for the parents of the proband to confirm their genetic status and to allow reliable recurrence risk counseling.
Note: If a pathogenic variant has not been identified in the proband, other testing options for the parents can be considered (e.g., mean corpuscular volume, erythrocyte adenosine deaminase activity, and/or fetal hemoglobin concentration).
If the pathogenic variant identified in the proband is not identified in either parent, the following possibilities should be considered:
The proband has a
de novo pathogenic variant. Note: A pathogenic variant is reported as "
de novo" if: (1) the pathogenic variant found in the proband is not detected in parental DNA; and (2) parental identity testing has confirmed biological maternity and paternity. If parental identity testing is not performed, the variant is reported as "assumed
de novo" [
Richards et al 2015].
The proband inherited a pathogenic variant from a mosaic parent. Parental germline mosaicism is suggested in a family described by
Cmejla et al [2000] in which neither parent of two affected sibs had the DBA-causing pathogenic variant identified in the affected sibs. Note: Testing of parental leukocyte DNA may not detect all instances of somatic mosaicism and will not detect a pathogenic variant that is present in the germ cells only.
The proband inherited a DBA-causing pathogenic variant from a parent who subsequently developed somatically acquired loss of heterozygosity with preferential loss of the chromosome with the DBA-causing pathogenic variant. This scenario may cause a false negative molecular result when testing leukocyte DNA (see
Molecular Pathogenesis) [
Venugopal et al 2017,
Garelli et al 2019].
The family history of some individuals diagnosed with DBA may appear to be negative because of failure to recognize the disorder in family members, reduced penetrance, early death of the parent before the onset of symptoms, or late onset of the disease in the affected parent. Therefore, an apparently negative family history cannot be confirmed unless molecular genetic testing has demonstrated that neither parent is heterozygous for the pathogenic variant identified in the proband.
Sibs of a proband. The risk to the sibs of the proband depends on the clinical/genetic status of the proband's parents:
If a parent of the proband is affected with autosomal dominant DBA and/or is known to have the pathogenic variant identified in the proband, the risk to the sibs of inheriting the pathogenic variant is 50%.
The penetrance of DBA in heterozygous sibs is high but may vary somewhat depending on the familial pathogenic variant (see
Penetrance). In affected heterozygous sibs, the clinical manifestations of DBA are unpredictable and can range, in the same family, from typical and atypical DBA phenotypes to a severe form presenting with fetal anemia resulting in nonimmune hydrops fetalis (see
Clinical Description).
If the DBA-causing pathogenic variant found in the proband is not detected in the leukocyte DNA of either parent, the recurrence risk to sibs is presumed to be slightly greater than that of the general population for one of two possible reasons:
Parental germline mosaicism for the DBA-causing pathogenic variant [
Cmejla et al 2000]; or
A false negative result in a parent due to preferential loss of the chromosome with the DBA-causing pathogenic variant (see
Molecular Pathogenesis).
If the parents have not been tested for the DBA-causing pathogenic variant but are clinically unaffected, sibs are still presumed to be at increased risk for DBA for one of two possible reasons:
Offspring of a proband. Each child of an individual with autosomal dominant DBA has a 50% chance of inheriting the DBA-causing pathogenic variant.
Other family members. The risk to other family members depends on the genetic status of the proband's parents: if a parent has a DBA-causing pathogenic variant, the parent's family members may be at risk.
X-Linked Inheritance – Risk to Family Members
Parents of a male proband
The father of a male with GATA1- or TSR2-related DBA will not have the disorder nor will he be hemizygous for the pathogenic variant; therefore, he does not require further evaluation/testing.
In a family with more than one affected individual, the mother of an affected male is an obligate heterozygote. Note: If a woman has more than one affected child and no other affected relatives and if the GATA1 or TSR2 pathogenic variant cannot be detected in her leukocyte DNA, she most likely has germline mosaicism. (No data on the possibility or frequency of germline mosaicism in the mother are available.)
If a male is the only affected family member (i.e., a simplex case), the mother may be a heterozygote, the affected male may have a de novo
GATA1 or TSR2 pathogenic variant (in which case the mother is not a carrier), or the mother may have somatic/germline mosaicism. (The frequency of de novo pathogenic variants is not currently known.)
Molecular genetic testing of the mother is recommended to confirm her genetic status and to allow reliable recurrence risk assessment.
Sibs of a male proband. The risk to sibs of a male proband depends on the genetic status of the mother:
If the mother of an affected male has a GATA1 or TSR2 pathogenic variant, the chance of transmitting it in each pregnancy is 50%.
If the proband represents a simplex case (i.e., a single occurrence in a family) and if the GATA1 or TSR2 pathogenic variant cannot be detected in the leukocyte DNA of the mother, the risk to sibs is presumed to be low but greater than that of the general population because of the possibility of maternal germline mosaicism.
Offspring of a male proband. Affected males transmit the GATA1 or TSR2 pathogenic variant to all of their daughters and none of their sons.
Other family members. The maternal aunts and maternal cousins of a male proband may be at risk of having a GATA1 or TSR2 pathogenic variant.
Note: Molecular genetic testing may be able to identify the family member in whom a de novo pathogenic variant arose, information that could help determine the genetic risk status of the extended family.
Heterozygote detection. Identification of female heterozygotes is possible once a GATA1 or TSR2 pathogenic variant has been identified in an affected family member.
Note: Females who are heterozygous for X-linked DBA will usually not be affected.
Prenatal Testing and Preimplantation Genetic Testing
Once the DBA-causing pathogenic variant has been identified in an affected family member, prenatal and preimplantation genetic testing for DBA are possible.
Differences in perspective may exist among medical professionals and within families regarding the use of prenatal testing. While most centers would consider use of prenatal testing to be a personal decision, discussion of these issues may be helpful.
Molecular Genetics
Information in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.
Table A.
Diamond-Blackfan Anemia: Genes and Databases
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Data are compiled from the following standard references: gene from
HGNC;
chromosome locus from
OMIM;
protein from UniProt.
For a description of databases (Locus Specific, HGMD, ClinVar) to which links are provided, click
here.
Table B.
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105650 | DIAMOND-BLACKFAN ANEMIA 1; DBA1 |
180468 | RIBOSOMAL PROTEIN L35A; RPL35A |
180472 | RIBOSOMAL PROTEIN S17; RPS17 |
300945 | TSR2 RIBOSOME MATURATION FACTOR; TSR2 |
300946 | DIAMOND-BLACKFAN ANEMIA 14 WITH MANDIBULOFACIAL DYSOSTOSIS; DBA14 |
305371 | GATA-BINDING PROTEIN 1; GATA1 |
602412 | RIBOSOMAL PROTEIN S24; RPS24 |
603474 | RIBOSOMAL PROTEIN S19; RPS19 |
603632 | RIBOSOMAL PROTEIN S10; RPS10 |
603633 | RIBOSOMAL PROTEIN S29; RPS29 |
603634 | RIBOSOMAL PROTEIN L5; RPL5 |
603658 | RIBOSOMAL PROTEIN S7; RPS7 |
603674 | RIBOSOMAL PROTEIN S15a; RPS15A |
603685 | RIBOSOMAL PROTEIN S28; RPS28 |
603701 | RIBOSOMAL PROTEIN S26; RPS26 |
603702 | RIBOSOMAL PROTEIN S27; RPS27 |
603704 | RIBOSOMAL PROTEIN L26; RPL26 |
604174 | RIBOSOMAL PROTEIN L15; RPL15 |
604175 | RIBOSOMAL PROTEIN L11; RPL11 |
604179 | RIBOSOMAL PROTEIN L18; RPL18 |
606129 | DIAMOND-BLACKFAN ANEMIA 2; DBA2 |
606164 | DIAMOND-BLACKFAN ANEMIA 15 WITH MANDIBULOFACIAL DYSOSTOSIS; DBA15 |
607526 | RIBOSOMAL PROTEIN L27; RPL27 |
610629 | DIAMOND-BLACKFAN ANEMIA 3; DBA3 |
612527 | DIAMOND-BLACKFAN ANEMIA 4; DBA4 |
612528 | DIAMOND-BLACKFAN ANEMIA 5; DBA5 |
612561 | DIAMOND-BLACKFAN ANEMIA 6; DBA6 |
612562 | DIAMOND-BLACKFAN ANEMIA 7; DBA7 |
612563 | DIAMOND-BLACKFAN ANEMIA 8; DBA8 |
613308 | DIAMOND-BLACKFAN ANEMIA 9; DBA9 |
613309 | DIAMOND-BLACKFAN ANEMIA 10; DBA10 |
614900 | DIAMOND-BLACKFAN ANEMIA 11; DBA11 |
615550 | DIAMOND-BLACKFAN ANEMIA 12; DBA12 |
615909 | DIAMOND-BLACKFAN ANEMIA 13; DBA13 |
618310 | DIAMOND-BLACKFAN ANEMIA 18; DBA18 |
618312 | DIAMOND-BLACKFAN ANEMIA 19; DBA19 |
618313 | DIAMOND-BLACKFAN ANEMIA 20; DBA20 |
618315 | RIBOSOMAL PROTEIN L35; RPL35 |
Molecular Pathogenesis
Ribosomes, consisting of a small 40S subunit and a large 60S subunit, catalyze protein synthesis. Small and large subunits are composed of four RNA species and approximately 80 structurally distinct ribosomal proteins (RPs). The proteins encoded by RPS19, RPS24, RPS17, RPS15, RPS7, RPS27A, RPS10, and RPS26 belong to the small ribosomal subunit, whereas those encoded by RPL5, RPL11, RPL26, RPL35A, and RPL36 are components of the large ribosomal subunit.
RPS19 protein has been demonstrated to play an important role in 18S rRNA maturation in yeast and in human cells [Léger-Silvestre et al 2005, Choesmel et al 2007, Flygare et al 2007, Idol et al 2007]. Similarly, alterations of pre-RNA processing of small or large RP subunit synthesis were demonstrated in human cells with RPS24 and RPS7 deficiency and with RPL35A, RPL5, RPL11, and RPL26 deficiency, respectively, further indicating that DBA is a disorder of ribosomes [Choesmel et al 2008, Farrar et al 2008, Gazda et al 2008, Gazda et al 2012]. Deficiency of RPS19 and RPL35A was shown to cause increased apoptosis in hematopoietic cell lines and in bone marrow cells [Farrar et al 2008, Miyake et al 2008], and imbalance of the p53 family proteins has been suggested as a mechanism of abnormal embryogenesis and anemia in zebrafish on perturbation of RPS19 expression [Danilova et al 2008].
Mechanism of disease causation. Rarely, missense variants may act in a dominant-negative manner, but haploinsufficiency of a ribosomal protein is the most common mechanism. Evidence suggests that ribosomal stress due to ribosome deficiency leads to stabilization of p53 and consequent p53-mediated cell cycle arrest or apoptosis. Furthermore GATA1, a critical erythroid transcription factor, has a complex 5' UTR and is poorly translated when ribosomal proteins are deficient. This can explain why GATA1 pathogenic variants result in a DBA phenotype [Ludwig et al 2014].
Gene-specific laboratory technical considerations. Revertant mosaicism (e.g., acquired uniparental disomy ablating a de novo
RPS19 pathogenic variant) has rarely been observed to account for spontaneous remission in individuals with DBA [Venugopal et al 2017, Garelli et al 2019].
Table 5.
Diamond-Blackfan Anemia: Gene-Specific Laboratory Considerations
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- 1.
Genes from Table 1 in alphabetic order