Clinical characteristics.

Holt-Oram syndrome (HOS) is characterized by upper-limb defects, congenital heart malformation, and cardiac conduction disease. Upper-limb malformations may be unilateral, bilateral/symmetric, or bilateral/asymmetric and can range from triphalangeal or absent thumb(s) to phocomelia. Other upper-limb malformations can include unequal arm length caused by aplasia or hypoplasia of the radius, fusion or anomalous development of the carpal and thenar bones, abnormal forearm pronation and supination, abnormal opposition of the thumb, sloping shoulders, and restriction of shoulder joint movement. An abnormal carpal bone is present in all affected individuals and may be the only evidence of disease. A congenital heart malformation is present in 75% of individuals with HOS and most commonly involves the septum. Atrial septal defect and ventricular septal defect can vary in number, size, and location. Complex congenital heart malformations can also occur in individuals with HOS. Individuals with HOS with or without a congenital heart malformation are at risk for cardiac conduction disease. While individuals may present at birth with sinus bradycardia and first-degree atrioventricular (AV) block, AV block can progress unpredictably to a higher grade including complete heart block with and without atrial fibrillation.

Diagnosis/testing.

The diagnosis of HOS is established in a proband with a preaxial radial ray anomaly and a personal or family history of cardiac septation and/or conduction defects. More than 70% of individuals who meet strict clinical diagnostic criteria have an identifiable heterozygous pathogenic variant in TBX5.

Management.

Treatment of manifestations: Management involves a multidisciplinary team of specialists in medical genetics, cardiology, orthopedics, and hand surgery. Treatment for arrhythmias may require medication, surgery, and/or pacemaker implantation. Pharmacologic treatment for individuals with pulmonary hypertension. Cardiac surgery for congenital heart defects is standard; affected individuals and families are also likely to benefit from programs providing social support to those with limb anomalies.

Prevention of secondary complications: A cardiologist can assist in determining the need for anticoagulants and antibiotic prophylaxis for bacterial endocarditis.

Surveillance: Annual EKG for all affected individuals, annual Holter monitor for individuals with known conduction disease, and echocardiogram every one to five years for those with septal defects or as directed by a cardiologist.

Evaluation of relatives at risk: Presymptomatic diagnosis and treatment is warranted in relatives at risk to identify those who would benefit from appropriate cardiac management.

Pregnancy management: Affected women who have not undergone cardiac evaluation should do so prior to pregnancy or as soon as the pregnancy is recognized; those with a known history of a structural cardiac defect or cardiac conduction abnormality should be followed by a cardiologist during pregnancy.

Genetic counseling.

HOS is inherited in an autosomal dominant manner. Approximately 85% of affected individuals have HOS as the result of a de novo pathogenic variant. Offspring of an affected individual are at a 50% risk of being affected. In pregnancies at 50% risk, detailed high-resolution prenatal ultrasound examination may detect upper-limb malformations and/or congenital heart malformations. Prenatal molecular genetic testing may be used to confirm a diagnosis if the TBX5 pathogenic variant has been identified in an affected relative.

Suggestive Findings

Holt-Oram syndrome (HOS) should be suspected in individuals with the following limb anomalies, cardiac findings, and family history:

• Upper-limb malformation involving the carpal bone(s) and, variably, the radial and/or thenar bones
  • Upper-limb malformations may be unilateral, bilateral/symmetric, or bilateral/asymmetric.
  • An abnormal carpal bone, present in all affected individuals and identified by performing a posterior-anterior hand x-ray [Poznanski et al 1970, Basson et al 1994], may be the only evidence of disease.
• Congenital heart malformation, most commonly ostium secundum atrial septal defect (ASD) and ventricular septal defect (VSD), especially those occurring in the muscular trabeculated septum
• Cardiac conduction disease
• Family history of a first-degree relative with a congenital heart defect or cardiac conduction disease

Note: Congenital malformations involving the following structures or organ systems are not typically within the spectrum of HOS and should prompt the clinician to consider alternate diagnoses: ulnar ray only, kidney, vertebra, craniofacies, auditory system (ear malformations ± hearing loss), lower limb, anus, and eye.

Establishing the Diagnosis

The diagnosis of Holt-Oram syndrome is established in a proband with either a preaxial radial ray anomaly and a personal or family history of cardiac septation and/or conduction defects or, if clinical findings are insufficient, a heterozygous pathogenic (or likely pathogenic) variant in TBX5 identified by molecular genetic testing (see Table 1).

Molecular testing approaches can include single-gene testing and – if the phenotype includes features that are atypical for Holt-Oram syndrome – a multigene panel. Though rare, chromosome rearrangements involving 12q24 have been reported in individuals with Holt-Oram syndrome [Li et al 1997, Basson et al 1999].

• Single-gene testing. Sequence analysis of TBX5 detects small intragenic deletions/insertions and missense, nonsense, and splice site variants; typically, exon or whole-gene deletions/duplications are not detected. Perform sequence analysis first. If no pathogenic variant is found, perform gene-targeted deletion/duplication analysis to detect intragenic deletions or duplications.
• A multigene panel that includes TBX5 and other genes of interest (see Differential Diagnosis) is most likely to identify the genetic cause of the condition while limiting identification of variants of uncertain significance and pathogenic variants in genes that do not explain the underlying phenotype. 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. (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 this disorder a multigene panel that also includes deletion/duplication analysis is recommended (see Table 1).
  For an introduction to multigene panels click here. More detailed information for clinicians ordering genetic tests can be found here.

Clinical Description

Holt-Oram syndrome is characterized by upper-limb defects, congenital heart malformation, and cardiac conduction disease [Holt & Oram 1960].

Upper-limb malformations may be unilateral, bilateral/symmetric, or bilateral/asymmetric and can range from triphalangeal or absent thumb(s) to phocomelia, a malformation in which the hands are attached close to the body; intermediate presentations resulting from abnormal development of the bones involved may also be observed. Other upper-limb malformations can include unequal arm length caused by aplasia or hypoplasia of the radius, fusion or anomalous development of the carpal and thenar bones, abnormal forearm pronation and supination, abnormal opposition of the thumb, and sloping shoulders and restriction of shoulder joint movement.

While all individuals have an upper-limb defect, the broad range of severity of these findings is such that some individuals with the mildest upper-limb malformations and mild or no congenital heart malformation may escape diagnosis. These individuals may only be diagnosed when a more severely affected relative is born or when symptoms develop in middle age as a result of cardiac abnormalities such as pulmonary hypertension, high-grade atrioventricular block, and/or atrial fibrillation. Cardiac conduction disease can be progressive.

A congenital heart malformation is present in 75% of individuals with HOS and most commonly involves the septum. Atrial septal defect (ASD) and ventricular septal defect (VSD) can vary in number, size, and location. ASDs can present as a common atrium and are often associated with cardiac chamber isomerism; that is, the defining features of the cardiac chambers, based on their anatomic location, are altered (e.g., what may be considered right atrium based on its anatomic location may not have the atrial appendage morphology typical of the right atrium).

Some individuals with severe congenital heart malformation may require surgery early in life to repair significant septal defects [Sletten & Pierpont 1996].

Other individuals may have complex congenital heart malformations [Faria et al 2008, Baban et al 2014, Barisic et al 2014]; conotruncal malformations, though observed in HOS, are not common and may be caused by other genetic defects.

Cardiac conduction disease. Individuals with HOS with or without a congenital heart malformation are at risk for cardiac conduction disease. While individuals may present at birth with sinus bradycardia and first-degree atrioventricular (AV) block, AV block can progress unpredictably to a higher grade including complete heart block with and without atrial fibrillation.

The natural history of HOS varies by individual and largely depends on the severity of the congenital heart malformation. Potential complications (which can be life threatening if not recognized and appropriately managed) include congestive heart failure, pulmonary hypertension, arrhythmias, heart block, atrial fibrillation, and infective endocarditis.

Genotype-Phenotype Correlations

It has been reported that pathogenic missense variants at the 5' end of the T-box (which binds the major groove of the target DNA sequence) are associated with more serious cardiac defects.

Pathogenic missense variants at the 3' end of the T-box (which binds the minor groove of the target DNA) result in more pronounced limb defects. Caution is warranted, however, in applying these population-based associations to individuals in whom pathogenic variants may not predict specific phenotypes [Basson et al 1999, Brassington et al 2003].

In addition, genotypes do not appear to predict the progressive hemodynamic course associated with any particular cardiac septal defect.

Penetrance

The upper-limb malformations in HOS are fully penetrant.

Congenital heart malformations occur in approximately 75% of affected individuals [Basson et al 1999]. Conduction defects may occur in the presence or absence of structural heart defects.

Nomenclature

HOS has been referred to as heart-hand syndrome, a nonspecific designation that could apply to any number of conditions with involvement of these structures.

Prevalence

HOS is the most common of the heart-hand syndromes. The estimated prevalence of HOS is between 0.7 and 1 per 100,000 births [Elek et al 1991, Barisic et al 2014].

HOS has been reported from a number of countries worldwide and in individuals of different backgrounds [Boehme & Shotar 1989, Yang et al 2000, Barisic et al 2014, Kimura et al 2015].

Other Diagnoses to Consider in the Differential Diagnosis of HOS

Disorders of unknown cause

• VACTERL (vertebral defects, anal atresia, cardiac malformation, tracheo-esophageal fistula with esophageal atresia, renal anomalies, and limb anomalies)

Teratogen exposure

• Thalidomide. Exposure to thalidomide in pregnancy places the fetus at risk for severe upper- and lower-limb defects (e.g., phocomelia, amelia), cardiac defects, and malformations in other systems not observed in HOS (renal, ocular, auditory, gastrointestinal, and craniofacial) [Matthews & McCoy 2003, McDermott et al 2005, Vianna et al 2013].
• Valproate. Exposure to valproate, particularly in the first trimester, places the fetus at risk for major congenital defects including congenital heart defects that can overlap those seen in HOS; however, the other malformations seen (e.g., polydactyly, spina bifida) are not features of HOS [McDermott et al 2005, Wyszynski et al 2005].

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed with Holt-Oram syndrome (HOS), the evaluations summarized in Table 3 (if not performed as part of the evaluation that led to the diagnosis) are recommended.

Treatment of Manifestations

The management of individuals with HOS optimally involves a multidisciplinary team approach with specialists in medical genetics, cardiology, and orthopedics, including a specialist in hand surgery.

A cardiologist can assist in determining the need for antiarrhythmic medications and surgery. Individuals with severe heart block may require pacemaker implantation. Pharmacologic treatment for affected individuals with pulmonary hypertension may be appropriate. Individuals with pulmonary hypertension and/or structural heart malformation may require tertiary care center cardiology follow up. Cardiac surgery, if required for congenital heart defect, is standard.

The orthopedic team may be able to guide individuals in decisions regarding surgery for improved upper-limb and hand function as well as physical and occupational therapy options. Those individuals born with severe upper-limb malformations may be candidates for surgery to improve function, such as pollicization (creation of a thumb-like digit by moving another digit into the thenar position) in individuals with thumb aplasia/hypoplasia [Vaienti et al 2009]. Children with severe limb shortening may benefit from prostheses as well as from physical and occupational therapy.

Individuals and families are also likely to benefit from programs providing social support to those with limb anomalies.

Prevention of Secondary Complications

A cardiologist can assist in determining the need for anticoagulants and antibiotic prophylaxis for bacterial endocarditis (SBE).

Surveillance

Agents/Circumstances to Avoid

Certain medications may be contraindicated in individuals with arrhythmias, cardiomyopathy, and/or pulmonary hypertension. People with such disorders require individual assessment by a cardiologist.

Evaluation of Relatives at Risk

It is appropriate to evaluate apparently asymptomatic older and younger at-risk relatives of an affected individual in order to identify as early as possible those who would benefit from appropriate cardiac management. Evaluations can include:

• Molecular genetic testing if the TBX5 pathogenic variant in the family is known;
• Echocardiography, EKG, and hand x-rays (anterior/posterior view) if the pathogenic variant in the family is not known.

See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.

Pregnancy Management

Pregnant women with HOS who have a known history of a structural cardiac defect or cardiac conduction abnormality should be followed by a multidisciplinary team (including a cardiologist) during pregnancy. Affected women who have not undergone cardiac evaluation should do so prior to pregnancy if possible, or as soon as the pregnancy is recognized.

See MotherToBaby for further information on medication use during pregnancy.

Therapies Under Investigation

Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.

Mode of Inheritance

Holt-Oram syndrome (HOS) is inherited in an autosomal dominant manner.

Risk to Family Members

Parents of a proband

• Some individuals diagnosed with HOS have an affected parent.
• A proband with HOS often has the disorder as the result of a heterozygous de novo TBX5 pathogenic variant. Up to 85% of cases are caused by a de novo pathogenic variant [Elek et al 1991], while approximately 15% of cases are familial [Barisic et al 2014].
• Recommendations for the evaluation of parents of a proband with an apparent heterozygous de novo pathogenic variant include echocardiography, EKG, and hand x-rays (anterior/posterior view) to determine their affected status. Alternatively, molecular genetic testing can be performed on the parents if the TBX5 pathogenic variant in the proband has been identified.
• If the pathogenic variant found in the proband cannot be detected in the leukocyte DNA of either parent, possible explanations include a de novo pathogenic variant in the proband or germline mosaicism in a parent. Presumed parental germline mosaicism has been reported [Braulke et al 1991].
• The family history of some individuals diagnosed with HOS may appear to be negative because of failure to recognize the disorder in family members, early death of the parent before the onset of symptoms, or late onset of the disorder in the affected parent. Therefore, an apparently negative family history cannot be confirmed unless appropriate clinical evaluation and/or molecular genetic testing has been performed on the parents of the proband.
• Note: If the parent is the individual in whom the pathogenic variant first occurred, the parent may be mildly/minimally affected.

Sibs of a proband. The risk to sibs of the proband depends on the genetic status of the proband's parents:

• If a parent of the proband is affected or has the TBX5 pathogenic variant identified in the proband, the risk to the sibs of inheriting the pathogenic variant is 50%. Significant intrafamilial clinical variability is observed.
• If the parents are clinically unaffected and the pathogenic variant found in the proband cannot be detected in the leukocyte DNA of either parent, the recurrence risk to the sibs of a proband appears to be low but slightly greater than the general population risk of approximately 1/100,000 because of the possibility of parental germline mosaicism.

Offspring of a proband

• Offspring of a proband are at 50% risk of inheriting the TBX5 pathogenic variant.
• Because of the effects of modifying genes and the significant variable expressivity observed in individuals with HOS, both among and within families with the same TBX5 pathogenic variant, the phenotype of affected offspring cannot be accurately predicted.

Other family members. The risk to other family members depends on the status of the proband's parents; if a parent is affected/has the pathogenic variant, the parent's family members are at risk.

Related Genetic Counseling Issues

See Management, Evaluation of Relatives at Risk for information on evaluating at-risk relatives for the purpose of early diagnosis and treatment.

Specific risk issues. Specific clinical risks of concern for at-risk family members are those related to life-threatening cardiac issues including congestive heart failure, arrhythmias, heart block, atrial fibrillation, pulmonary hypertension, and infective endocarditis.

Predictive testing for at-risk asymptomatic adult family members requires prior identification of the TBX5 pathogenic variant in the family.

Considerations in families with an apparent de novo pathogenic variant. When neither parent of a proband with an autosomal dominant condition has the pathogenic variant identified in the proband or clinical evidence of the disorder, the pathogenic variant is likely de novo. However, non-medical explanations including alternate paternity or maternity (e.g., with assisted reproduction) and undisclosed adoption could also be explored.

Family planning

• The optimal time for determination of genetic risk and discussion of the availability of prenatal/preimplantation genetic testing is before pregnancy.
• It is appropriate to offer genetic counseling (including discussion of potential risks to offspring and reproductive options) to young adults who are affected or at risk.

DNA banking. Because it is likely that testing methodology and our understanding of genes, pathogenic mechanisms, and diseases will improve in the future, consideration should be given to banking DNA from probands in whom a molecular diagnosis has not been confirmed (i.e., the causative pathogenic mechanism is unknown).

Prenatal Testing and Preimplantation Genetic Testing

For pregnancies known to be at increased risk for HOS

• Once the TBX5 pathogenic variant has been identified in an affected family member, prenatal testing for a pregnancy at increased risk and preimplantation genetic testing are possible.
• If the TBX5 pathogenic variant is identified in a fetus, molecular genetic testing should be followed by detailed ultrasound (US) evaluation.
• If the pathogenic variant in the family is not known, US examination evaluating for characteristic limb and cardiac manifestations (including fetal echocardiogram) is recommended. Note: A normal ultrasound examination does not eliminate the possibility of HOS in the fetus.

For pregnancies not known to be at increased risk for HOS. If a routine US examination has identified limb and cardiac manifestations characteristic of HOS, consider prenatal molecular genetic testing from a clinical laboratory that offers testing for TBX5 or custom prenatal testing for other disorders in the differential diagnosis (see Differential Diagnosis).

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.

Because of the significant variable expressivity observed in individuals with HOS both among and within families with the same pathogenic variant, the severity of upper-limb defects and congenital heart malformations cannot be accurately predicted by molecular genetic testing alone.

Revision History

• 23 May 2019 (sw) Comprehensive update posted live
• 8 October 2015 (me) Comprehensive update posted live
• 4 April 2013 (me) Comprehensive update posted live
• 4 January 2011 (me) Comprehensive update posted live
• 22 November 2006 (cd) Revision: array genomic hybridization and deletion/duplication testing clinically available
• 21 September 2006 (me) Comprehensive update posted live
• 20 July 2004 (me) Review posted live
• 23 December 2003 (cb) Original submission

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